He captioned it: 'Had an incredible visit @Childrens LA pediatric cancer research program, they are at the forefront of groundbreaking research that saves the lives of kids diagnosed with cancer.'Every dollar is so important-- join me in helping these amazing doctors, researchers and brave kids battling cancer.'He also urged fans to donate to the hospital and support him and his Team Flow partners.
Zac's team weren't the only celebs at the triathlon.
He jumped onto a cab, alongside Zac, for a moment during filming.
The actress, 21, rocked curly tresses while busting out a move on the New York City street for the skit.
Zac later made a statement with his voluminous blonde wig during another part of the segment, seemingly inspired by the eighties classic Fame.
They were joined by James Marsden, Oscar Nunez, Joel Mc Hale, Luke Hemsworth and Jamie Lee Curtis to name a few.
Zac will next be seen o the big screen with Hugh Jackman as P. Barnum in The Greatest Showman, out on Christmas Day.
You can't even imagine anyone else playing that role.