Growing up, Zack loved Halloween, and his father put a lot of effort into scaring him every year. At fourteen Zack found that Halloween didn't scare him anymore- only for his dad to successfully scare him again anyway.
After an incident on a boat ride up the Saskatchewan River with his parents, Zack developed a crippling phobia of fish that stays with him to this day.
Prior to moving to Danville - or at least the area of it where he currently resides - Zack was friends with a group of guys now referred to as The Lumbermaxes. Eventually, with Zack as their leader, they formed 'The Lumberzacks'; a lumberjack-themed boy-band that gained regional popularity after their hit song 'Chop Away at my Heart'. According to Zack, they started the band because his mother had a bunch of flannel.
He claims that the band collapsed due to the high-pressures of their lifestyle after a girl came between them- but that was a clear dramatization. His flashback reveals a much more childish and less intense version of the story in which his bandmates barely glance up from their video games when he says bye for the last time, with the girl he mentioned having walked between them in a line up for a brief second, causing a small argument before leaving.
Zack has since come to be deeply embarrassed by this part of his past and tried hard to hide it from his new friends.
Zack first meets Milo when he is on his way to attend his first day of school, with the pair meeting at the bus stop. After seeing several other students - including Bradley Nicholson, Chad Van Coff, and Melissa Chase - purposefully keep their distance from Milo, Zack questions the reasoning behind it and initially wonders if Milo is supposed to be a "tough guy." He soon learns that Milo is, in fact, the subject of ongoing mishaps due to Murphy's law, which Zack begins to experience as the two are forced to flee from a section of concrete pipe that has fallen off of a truck. The two are able to escape due to Milo's quick-thinking but are forced to chase the bus.
Zack and Milo endure several other calamities - an oil spill that catches fire, a pack of wolves, and a beehive that becomes stuck on the head of one of those wolves - as they continue the pursuit of their school bus. After they end up in the city sewers, Zack announces his intentions to go his own way, only to gain a new perspective on the unusual situation from Milo, who notes how much more exciting their morning has been than that of their classmates. The two are then caught in a flood caused by the absence of the pipe they escaped from previously, washed into a river, and then thrown off a cliff only to land on top of a flying saucer. However, as they are about to be apparently dissected by the aliens, Zack informs the extraterrestrials that they may become late for school, and the aliens then teleport the pair to their first-period classroom just in time. The pair is elated but then realize that their lunches have been destroyed, only to discover that Melissa has taken care of the situation due to starting a betting pool in which the different students on the bus bet food on whether or not Zack and Milo would make it to school on time.
In "Sunny Side Up", Zack teams up with Milo and Melissa for a science project involving creating a device that will enable an egg to survive a long fall intact. They are eventually successful, though only after destroying an inordinate number of eggs, and Zack and Melissa Chase take their last remaining egg and the device home with them. Zack then has a nightmare about the device being destroyed, but wakes up to find that it wasn't real; unfortunately, the egg is smashed before they can take part in the experiment. Fortunately, an egg Milo had put in his pocket earlier turns out to be intact, allowing them to test their device in front of the class. The device and the egg end up going through an insane amount of punishment after being hit by a delivery truck, but ultimately the egg lands safely-only to be eaten by Diogee after Zack's group is graded with an A.
In "Rooting for the Enemy", Zack has joined the Jefferson County Middle School Geckos football team and pleads with Milo and Melissa to attend his first game, which Milo gets permission to do since Coach Mitchell is convinced that the team will lose.
In "The Undergrounders", Zack and his friends become separated from their class while on a subway to the museum and end up coming across a subterranean group known as the Undergrounders. He's revealed to have claustrophobia, though he claims he's just claustro-avoidant, and thus avoids small spaces. When Diogee comes and leads the people to a subway train, Milo and Melissa suddenly being trapped in a cave-in. Zack is the one who gets them out safely, and fast enough.
In "The Doctor Zone Files", Zack and Melissa are invited to a The Doctor Zone Files marathon by Milo and his sister Sara Murphy in anticipation of going to see the new Doctor Zone Files movie. Milo and Melissa, while questioning whether Time Ape is an ape with a clock for a head or a clock with the body of an ape, get into a dispute with some hardcore Doctor Zone fans. When the two hit upon the idea that Time Ape is actually Doctor Zone's brother, the fans are disgusted, but Zack and Melissa are later proven right.
In "The Note", Zack and his friends attempt to recover the signature page from a bulk doctor's note for Milo, as otherwise he will have several unexcused absences and have to repeat seventh grade. After chasing the note through an office building, a parade and a recycling center, they get it but are stopped by Elliot, much to their annoyance. But he is soon be integrated, much to their shock and confusion.
In "Party of Peril", Zack and Melissa convince Milo's parents to throw him an actual birthday party as opposed to the limited affair he's had previously.
In "Worked Day", he and his class visit their parents for career day. They watch Milo's father at the water center- where a flood occurs, Melissa's father at the Fish Hatchery, where Milo starts a fire with water, and his mother at the Hospital, where an MRI machine becomes a super magnet.
In "The Wilder West", he, Milo, Melissa, and a Sara go to the Nowhere Desert Dude Ranch, while Sara wonders off to see if an episode of Doctor Zone was filmed there. While riding horses they are chased down by a girl named Jackie, who he develops a crush on. The three spend the day with her and it takes him surviving an avalanche, raging bull and flash flood to over Jackie. He eventually realizes that Jackie only brings them more danger and in the end, the two of them say their goodbyes.
In "Family Vacation", he and Melissa watch Diogee while the Murphys go on a road trip. They also relax in a pool.
In "Murphy's Lard", he, Milo and Melissa go to Lard World and learn that Melissa has a fear of roller coasters. They take her to the amusement park's largest roller coaster, greased thunder, where he immediately gets off when Melissa points out that they would be on a roller coaster with Milo and leaves the two to deal with Murphy's Law on a roller coaster. As they are about to lead he is hit with a goldfish in a plastic bag and freaks out.
In "Secrets and Pies", he tries to keep his past involvement as a singer (and title character) in a boy band from being discovered by Milo and Melissa. He ultimately fails when Veronica reveals it and they watch the music video for Chop Away at my Heart online.
In "Athledecamathalon", he, Milo, Melissa, Mort, and Chad participate in a combined scholastic and athletic event, which they just heard of, against the Middletown Middle School Middlemen, who knew about it for three months. Things go poorly until Murphy's Law makes it fair game for them. At the final event, he somehow winds up stuck in a volleyball net in a tree with a hotdog cart defending a hotdog from seagulls. But in the end, The Geckos are the final winner.
In "The Substitute", he describes their substitute science teacher, Ms. Baxter, as burnt out. He assists Milo with chemicals until a drop spills and the entire class, save for Milo and Melissa, panics. After Milo creates a Sentient Blob he, Milo and Melissa freeze the blob with fire extinguishers.
In "We're Going to the Zoo", Zack and the Murphy siblings chase down Brigette's t-shirts that were accidentally donated, only to discover that Brigette did intend to donate them.
In "School Dance", he, Milo and Melissa attend the school dance Amanda organizes. He and Melissa are able to have an eye on the party's coat check. Chad is able to convince him and Melissa that two men are vampire hunters out to kill Mr. Drako. The three confront them and the pair leave. After the band vanishes, Milo asks him, Melissa, and Mort to fill in.
In "Battle of the Bands", he, Milo, Melissa, and Mort form a band. At first, he just wants to use the contest as practice to get the other members used to perform in front of audiences. However he runs into his old band, now called The Lumbermaxes, and Max taunts him into wanting to win; which affects his behavior with his new band. As Lumbermax is performing he gets nervous and volunteers to play all the instruments himself until he realizes what he is doing. The band performs A Bumpy Ride Tonight and does well. Max even offering him to rejoin, but he turns a deaf ear to the former leader's rejection.
In "The Math Book", he goes with Melissa and Milo to school to get Melissa's math book. They get a key from Principal Milder but end up locking it in the classroom. They eventually get back into the room by going on "a quest", and finally are able to the key.
In "The Llama Incident", he and his friends are dangling over a cliff on a branch. During this time his friends tell him about the infamous Llama Incident. He is impressed and uses that story to form an idea to get to safety which he calls The Woodpecker Incident.
In "Missing Milo", he and his friends narrowly escape a wave of lava. After Milo vanishes, he and Melissa go looking for him. Diogee finds Milo's backpack and they are chased by Brick and Savannah, but they avid the time travelers with help from Scott. They go to Milo's house and see him in the pilot episode of Doctor Zone, filmed in 1965. He goes with Melissa, Sara, and Diogee to Melissa's house, where she has a room dedicated to Murphy's Law and keep seeing two figures in most of the backgrounds. The group heads to the home of Orton Mahlson, the creator of Doctor Zone, to see if he knows anything. He gives them a letter from Milo telling them to meet him at Jefferson County Middle School at 3:00 PM. they arrive and are greeted by King Pistachion and his forces. Milo, along with Dakota and Cavendish, arrives shortly after and the six put up a fight on until all of them, except Milo and Diogee, are taken captive. Luckily, Diogee pees on the king's current day self and his forces vanish.
In "Disaster of My Dreams", he practices with the band Just Getting Started while doing his regular school schedule.
In "A Clockwork Origin", he goes with his friends to V-Tech to show Victor Verliezer his app, which is supposed to add an armadillo to any picture but instead makes a high pitched sound. After finding out that Veriliezer's new invention, C.I.D.D., is not his they search for his real creator at a lumberjack festival. Zack is hesitant about going in because of the Lumberzacks, but no one recognizes him, with the exception of a security guard. They find C.I.D.D.'s creator, Clyde Rickenbacker, and the five of them run away from V-tech. After they reveal that Verliezer mocks his customers, they abandon his products and he his company goes belly up. Zack's armadillo app finally works.
In "Perchance to Sleepwalk", he goes camping with Milo and Melissa while his parents stay in a nearby resort. After Milo sleepwalks he and Melissa chase him while dealing with Murphy's Law. They catch up with him and bring Milo back to camp.
In "Some Like it Yacht", he goes on the school yacht and gets stranded on an island. He, Mr. Drako, and the rest of the student on board, with the exception of Bradley, patch up the boat and scout out the island for resources while the majority of the faculty went feral almost instantly.
In "Backward to School Night", he and his mom go to back-to-school-night along with Milo, Melissa and their dads. After their parents and Ms. Murawski are turned into toddlers, the children chase them around the school until Cavendish fixes the device that could turn them into adults again. He and his friends fall asleep from exhaustion while their parents watch them sleep.
In "World Without Milo", Zack protests Elliot's rudeness to Milo; in the alternate timeline in which Milo no longer exists, he and Melissa have not met until they both encounter Elliot, who is the only one to remember Milo's existence.
In "The Race", he and Melissa help Milo deal with Murphy's Law during a race, by using his backpack to help Milo having everything he needs. While for the whole race, they're unable to do that well, in the end, they finally can build for him a helpful thing - a makeshift finish line.
In "Love Toboggan", he and Melissa go skiing with Milo and his father. During the day they are nearly crushed by a giant snowman, chased down the mountainside by an avalanche, and flung from the ski resort to town on a toboggan. They crash into Sara and Neal before the toboggan becomes jet propulsion on a boiler. After Diogee disconnects the boiler from the sleigh, the three leave the older teenagers alone.
In "The Island of Lost Dakotas", he, Melissa and Milo are going to see Hamosaur with Zack impatiently waiting for Milo to find his shoes. He gives Milo a pair that has laces, which Milo reluctantly takes. On the way there he and Melissa are entangled in Milo's shoelaces and stuck to Hamosaur's tail. With Milo's quick thinking they are saved.
In "Fungus Among Us", he, Milo and Melissa are falling out of the sky when their hot air balloon popped, but are saved by Cavendish and Dakota who then take Milo with them to 1965 with the two betting that it would not end well. During that time they are taken prisoner by the Pistachions and replaced by Pistachions in human costumes. They are locked in a cage at Lard World with Milo's family.
In "Milo Murphy's Halloween Scream-A-Torium!", he is the only one among his friends and Sara not dressed for the holiday. He says he grew out of it and checks out the decommissioned truck Milo had turned into a haunted house. He gets separated from the girls and realized the truck, which has no breaks or steering, has moved and is now dangling over a cliff. He and Milo pull the truck off the cliff before it rolls downhill dragging Elliot with them. They make their way through various warehouses before plummeting off another cliff. Parachutes then break their fall and they land in the courtyard of Jefferson County Middle School. He has regained his love of Halloween once again. While Milo, Sara and Melissa runaway in terror at the sight of an exhausted Elliot, he only does so when his father shows up dressed as a fish; his worst fear.
In "A Christmas Peril", he and Melissa help Milo and Sara pick up the extended Murphy family during Christmas Eve while a blizzard is forming. The group is stranded when their car is buried under snow. They then take a horse-drawn carriage until it winds up stuck in a tree. They make their way to the mall, where they run into Milo and Sara's parents and have dinner at the Chinese restaurant. His parents join him along with Melissa's father, Mort, and Amanda.
In "The Phineas and Ferb Effect", Zack, alongside Melissa, meets Buford and Baljeet in a Pistachion prison. The four of them escape together after Martin causes a Murphy's law related disaster, and go on to meet Candace, Phineas, Ferb, and eventually Milo. The group travels to one of Phineas and Ferb's workshops, where they eventually build the Murphy's Law Suit but are inadvertently captured once again. Zack is eventually turned into a Pistachion by the M.U.L.C.H. machine, but is returned to normal after the Pistachions are defeated.
In "Snow Way Out", he and Milo are swept away from the bus stop by a giant snow ball. As they get to school they end up at a mideavil festival and they break free, only for the snowball to pick up deadly weapondry to fling at them. They are joined by Diogee and get stranded on an iceberg. As they are climbing a rope to the Maple Street bridge they are swallowed by a whale. They get out with a makeshift slingshot and realize they missed first bell. They run into Cavendish and Dakota and ask them to take them back five minutes only to learn the two were banned from time travel. The former time travelers give him and Milo the time machine to use and they make it to class.
In "Teacher Feature", he and Melissa are helping Milo with a chemistry safety demonstration when Murphy's Law causes the floor to open and Ms. Murawski to fall into the Sewers. Their teacher goes in after the desk. Both are saved by Scott and she thanks him with dinner. He and his friends spend the day teaching Scott how to behave and shadow him to ensure this. At the end the two decade to remain friends.
In "Game Night", he, Milo, Melissa and Diogee decide to play a board game and finally finish it. They are joined by Sara, Neal, Cavendish, Dakota and Milo’s parents. After the game is rendered unusable, they make a makeshift game out of any game they can find. As they are a turn away from finishing, a deadly vortex opens up and sucks them in. Luckily they finish in another dimension.
In "Pace Makes Waste", he goes with Milo and Melissa to a charity race for llamas. They run into Elliot on the way to the announcer’s booth and ignore him. When the pacer Elliot and Milo are in suddenly gains a rocket engine and takes off with the racers in tow for the “warmup lap”, he becomes the announcer when the original leaves. He does badly at first due to not seeing the cars from a distance, but things improve when Melissa hacks into various cameras around town.
In "Lady Krillers", he and his friends learn that Tobias Trollhammer is not going to be in the next Krillhunter film as it is a female lead reboot. When they learn Tobias’ fears of being out of the job the three dress him up as a woman to audition for the lead. However Tobias is exposed but after giving a speech about how he is the franchise he is cast as the villain, giving him and his friends mixed feelings on the outcome.
In "Doof's Day Out", he goes with his class to the Natural History Museum to check out the digestive system exhibit. However his claustroavoidence acts up, resulting in Doofenshmirtz and his friends constructing a go cart out of display organs to get him out fast.
In "The Ticking Clock", he, along with Milo and Melissa, help fix up Ol’Betsy with the help of Clyde Rickenbacker and C.I.D.D. before 5:00 or else the city will sell the land to Victor Verliezer, who plans to tear it down and put up a new digital clock in its place. They succeed.
In "Managing Murphy's Law", he and the rest of Just Getting Started by Amanda to perform in the Forget the Llamas, Save the Alpacas benefit concert. As they prepare, they try to think of a new band name. By the time of the concert they chose to keep their name.
In "Sick Day", he and Melissa bring Milo his homework while he is sick at home.
In "Field of Screams", he asks Milo and Melissa to help him with his uncle Cornelius’ farm. His father doubts he could do it but he and his friends manage to get the chores done despite Murphy's Law. He proves his father wrong and gets into the tabloids.
In "Spy Little Sister!", he and Milo compete in the Build-A-Bot Contest. However there robot turns sentient and evil when they put Doof’s lightbulb in it. Luckily it is stopped by Savannah and Melissa.