Zizou reckons the Portuguese wouldn't score nearly as many goals if it wasn't for the Barca man driving him onZinedine Zidane has put Cristiano Ronaldo's incredible goalscoring feats down to his rivalry with Lionel Messi.
The Real Madrid superstar recently passed 500 career goals for club and country, in 754 matches, while he has 324 strikes in 309 games for Los Blancos.
Messi has so far amassed 418 goals for Barca, in 493 outings, including 73 strikes in his record-breaking campaign of 2011-12.
Ronaldo overtook Spanish legend Raul, who was the club's all-time leading scorer on 323 goals, and Zidane, who currently coaches Real's B team, thinks the forward benefits from Messi being around at the same time.
"Fifty to 55 goals per season is just not human," Zidane told French TV programme Canal Football Club.
"But you should see him at training. At training, he's a guy who every ball, every match, every corner... he wants to score, he wants to win.
"And when he scores he does the same thing he does in a match. He's happy and he falls to his knees [to celebrate]... it's incredible.
"There's a feature in all of that and it's that there's another player opposite who pushes him. That's to say the rivalry he has with Messi.
"He doesn't need that [to perform]. But what keeps him scoring 55 to 60 goals a season is the fact that he says to himself 'this year I have to score one more than the other guy every time.'"
Zidane has also played down reports of a potential switch to Paris Saint-Germain for Ronaldo.
The Portuguese has been linked with a big-money move to the French capital, but Zizu doubts if that will be the case.
"He's the best player in the world so it's normal that you'd want to sign Ronaldo," the 1998 World Cup winner added.
"But he's comfortable at Real... since Raul left he's really become the other legend of the club."