Despite a disappointing display from Madrid, they retained momentum at the top of La Liga as Ronaldo netted a penalty and a thumping header to clinch victory at the Santiago Bernabeu.
The Portugal international received his fair share of criticism earlier this campaign, but Zidane was quick to point to a return to form for his talismanic forward, who already scored a hat-trick against Atletico Madrid last week.
"Cristiano is like that, he can score at any time," Zidane said. "When he does not score, people think that he has not played well.
"He played well with Karim [Benzema] in the middle and dropped out to the wing, working hard and he is back on form."
Zidane also defended James Rodriguez as the Colombian came in for the injured Gareth Bale, having previously struggled for game time.
"I do not consider him to be disinterested," he added.
"James played well, as did the others. He may lack a bit of rhythm, but I am happy that he got some playing time."