When Zac was asked about training for his upcoming Marine role, he said, "By the end of the movie I didn't recognize myself. You hear about guys like Christian Bale who dive into it and are really able to transform. I've always wondered if I had the willpower to actually do it. And I'll always have pride around the sense that I can."
Efron adds, "I was never a natural at anything, but I could always outwork everybody."
Read the full story in Men's Health, on newsstands April 17.