In A Hawaiian inspired button-down with cuffed sleeves, the lanky young actor appeared on the red carpet of the WB Networks' 2004 All Star summer Party.
A year laster and still without any noticeable muscle definition, Zac sported another button down with cuffed sleeves at the breakfast with the cast and crew of 'High School Musical'.
The teenage heart throb flexed his muscles on the red carpet at the premiere of 'High School Musical 2'.
At the 2007 Madrid ' Hairspray' Photocall, we begin to see the peak of slight muscle definition in what later becomes Zac's infamous athletic body.
Still with his muscles on the lean side, Zac rocked a fitted mode-sleeve button down and vest to the 2008 Teen Choice Awards.
Tanned and visibly chiseled a year later at the Teen Choice Awards, Zac opted for his go-to classic button down with cuffed sleeves look.
While visiting Maui in June 2010, the young stud showed off his hot physique after taking a dip.
Zac soaked up the sun in Maui in June 2010 - shirtless of course.
In 2011, Zac modestly showed off his biceps in a simple black tee while sitting court side at a Lakers game.
Zac relaxed to music shirtless at his Sydney hotel in April 2012.
While filming his 2014's 'Bad Neighbors', the actor frequently showed off his incredibly buff body on and off the big screen.
With the star being in the best shape then ever before, he couldn't resist showing off his chiseled abs and biceps on the 2014 MTV Movie Awards stage.
While filming 'We are your friends', Zac showed off his sculpted bod again while running on the beach.
Acting out a scene from his new film 'Bad Neighbors 2' at the 2015 MTV Movie Awards, the stud shows off his hot bod once again under a green fatigue jacket.
Zac was spotted walking the streets of Los Angeles last year flexing his muscles without even trying.
While filming his newest movie 'Baywatch' Zac shows off all of his hard training work by shooting shirtless scenes showing of his incredibly ripped bod.