He is portrayed by Dylan Sprouse.
Like his brother, Zack is about four feet tall with short blonde hair at the start of the series. He generally wears long-sleeved shirts with t-shirts over top, and skater pants or shorts along with skater shoes. Of the two, he generally appears to be far more laid back than his brother, who usually wears more formal clothing. Before the start of The Suite Life on Deck, Zack grew his hair longer, to be around shoulder length. As the series progresses, Zack grows to around five-foot-ten tall, and cuts his hair back to a much shorter length.
Zack is a "player" and a "ladies' man" when it comes to girls. However, when it comes to schoolwork, Zack is not nearly as smart as Cody, and is described as lazy by Mr. Forgess in the episode "Smart & Smarterer". He's the more athletic of the twins and likes to play basketball, baseball, football, and dancing. He likes to be in the limelight and often tries to take credit for other people's accomplishments. He can be very petty when it comes to money and sometimes uses Cody for get-rich-quick schemes. Even though he insults and uses Cody, he is shown to be protective when other people are mean to him. Unlike his brother Cody, who loses most of his prankster antics, Zack is still fond of pranking people throughout both of the series regardless of the often high consequences and already knowing he will be the first person blamed. When it comes to causing trouble, he seemingly has an affinity for it.
Despite his tough-guy attitude, Zack is the more sentimentally attached of the twins. He always misses Cody when he's gone and often feels bored without him. He also clung to his mother's legs during the first episode of The Suite Life on Deck, crying, "Mommy, don't go!"