Zidane won the Champions League at first attempt last season.
"Zidane was key last season for us. After his arrival he made us work harder and more efficiently," said Ronaldo.
"He's a great professional and an excellent person. In my opinion the tranquility he transmits to the players is one of his key strengths. What coach wins the Champions League just six months after taking over a team? Zidane deserves a huge amount of credit and I'm delighted he's with us.
"Playing for Real Madrid there is always the expectation of winning major titles. The Champions League has always been a special competition for the club. We've won it more that any other football club and there is a unique connection with the competition. Our aim is to win the twelfth come June 2017."