Zack was not originally part of Final Fantasy VII's story during development, but scenario writer Kazushige Nojima wanted to bring a sense of mystery to the title, and created the character to help complicate Cloud's backstory.

[2] Nojima had always planned for Cloud's memories of his life to be proven false as the game went on, but he had not decided on how to implement this until he hit on the character of Zack.

[3] For Final Fantasy VII: Advent Children, Zack made only a couple of brief appearances, and as such, was not difficult to animate; the team had also acquired his design early in production, allowing modeling of his character to be taken care of.

[2][8] Throughout the game, the staff decided to use a blue sky in cutscenes to represent Zack, while other features in such scenes are meant to symbolize his connections.

[17] Flashbacks reveal that both Zack and Cloud battled Sephiroth after he burned down the town of Nibelheim upon discovering he was born from a scientific experiment.

Zack also appears during the chapter covering the Nibelheim incident, and later as a boss character when he and Cloud are fugitives from Shinra and are being pursued by the Turks.

[24][25] He and Sephiroth learn that both Angeal and Genesis were the result of a Shinra experiment called "Project G", where they were injected with Jenova cells prior to being born in an effort to create perfect SOLDIERs.

[35] Zack has served as the basis for several forms of merchandise, such as being pictured on the Final Fantasy VII 10th Anniversary Potion soft drink cans.

[36][37] Outside the Final Fantasy VII series, Zack is an unlockable character in the PlayStation version of the fighting game Ehrgeiz, where is playable in arcade, versus, and minigame events.

He is featured prominently in the Olympus Coliseum (which is where Cloud often appeared in previous installments), commonly participating in tournaments in order to achieve his dream of becoming a hero.

[40] Zack appears at the end of Final Fantasy VII Remake during a flashback scene, where he survives the ambush by Shinra forces and continues dragging Cloud toward Midgar.

He returns in Final Fantasy VII Rebirth, which explores the alternate timeline, in which Zack helps Elmyra look over a comatose Cloud and Aerith as the end of the world approaches.

[47] 1UP.com's Jeremy Parish agreed with Clements, arguing that Zack's story contrasted with other RPG plots, calling it "the heart of the game".

[48] Kevin VanOrd from GameSpot labelled Zack a "likable and complex hero", arguing that he "transcends the usual spiky-haired heroism and teenage angst with an uncommon maturity that develops as the game continues".

[49] GameSpy's Gerald Villoria described Zack as "King of the Nice Guys", noting that even though he can be a "pretty hate-worthy character if you're the jaded type who mocks the typical Final Fantasy storyline", players who dislike him could come to appreciate him.

[51] Like other reviewers, RPGamer viewed him to have the "full, soulful carriage of a Final Fantasy hero" due to his personal conflicts, despite his "artfully teased hair and devil-may-care grin".

[53] GamesRadar's AJ Glasser commented that the way Zack obtains the Buster Sword and the way he gives it to Cloud is the "ultimate payoff" of Crisis Core, stating that the fact gamers know how the game will end is a serious detraction.

[54] When Ayaka finished the song "Why" for Crisis Core, she mentioned that she wanted to deliver it alongside Zack's fate "to the hearts of many people".

[55] IGN UK's Dave McCarthy noted how Zack's role in the Compilation of Final Fantasy VII evolved as the series developed, to the point of him getting his own game.

[56] Similarly, VideoGamer.com's Wesley Yin-Poole called Zack Cloud's "identical twin in all but hair colour" and complained about his personality being "annoying" during the first half of the game.

Eurogamer praised Zack's English voice actor for doing a good job, noting "his character's maturing and developing over the 15-hour storyline".

[66][67][68][69] The criticism from fans in regards to Pierce's performance as Zack resulted in websites noting that mods were created for the game to restore the original voice actors.