Holy abs!  

Zac Efron and Robert De Niro were spotted on the set of their new flick, "Dirty Grandpa," in Tybee, Georgia on Thursday. 

Efron looked tanned and toned as he flaunted his chiseled chest wearing nothing but yellow pants. De Niro, 71, definitely held his own alongside the heartthrob while sporting beige khakis and a matching bucket hat. 

The comedy will follow an uptight guy who is tricked into taking his perverted grandfather to Florida for spring break. 

Julianne Hough, Aubrey Plaza and Dermot Mulroney also star alongside the "High School Musical" star and the "Meet The Fockers" actor in the funny flick. 

Efron showed off his hot bod earlier this week while on the set wearing nude boxer briefs -- clearly the 27-year-old has no problem stripping down in the name of comedy! 

What do you think about Robert and Zac's shirtless shot? Tell toofab in the comment section below and click "Launch Gallery" above to see more shirtless stars! 

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