The 31-year-old Ronaldo, who along with team mate Gareth Bale is on the shortlist for the 2016 Ballon d'Or for the world's best player, has failed to score in four straight games at the Santiago Bernabeu stadium, a first in his Real career since joining in 2009.
He was jeered during Sunday's 2-1 win over Athletic Bilbao even though the result returned Zidane's side to the top of the table.
"I don't understand the jeers but at the same time, I was also jeered and it can happen," Zidane, who won the World Cup as a player with France as well as league titles with Juventus and Real, told reporters on Tuesday.
"The public demands a lot from the players and the Bernabeu is special. Cristiano knows that and is not concerned by it."
Bale and other team mates have come to Ronaldo's defence, arguing that he excels in other aspects of the game.
Zidane expects Ronaldo to rediscover his goalscoring touch soon.
"Of course I prefer if he scores two of three goals per game," Zidane said. "But I'm not worried because I know it will happen.
"He is not making his chances now but he will, soon he will do so and with calmness."
Zidane said that if Ronaldo, Bale and Karim Benzema are fit, they would always play but Portuguese's current form has sparked a debate about his place in the team.
"I have three stars and they are going to be very important for the team," Zidane said. "The others may play less but there are still as important to me. There are always going to be some that have less minutes than others. This is logical.
"For me, they are all important."
Real play at Cultural Leonesa in the first leg of their last-32 King's Cup tie on Wednesday.
(Reporting by Adriana Garcia, editing by Pritha Sarkar)
