After opening the scoring in the 53rd minute to become the top scorer across all competitions in Europe's top five leagues, Atletico Madrid attacking talisman Antoine Griezmann levelled matters five minutes later.
Zidane then opted to substitute Ronaldo for Karim Benzema just after the hour mark, as the derby was evenly poised at 1-1 at the Santiago Bernabeu.
Although Los Blancos had late chances to secure victory and stake a claim for second spot in LaLiga, Zidane's decision was questioned after the game, with the five-time Ballon d'Or winner in the form of his life.
"It was just to rest," Zidane said in reference to keeping Ronaldo fresh for their UEFA Champions League quarter-final with Juventus, as quoted by AS.
"We have many games, that's it. Sometimes he needs to rest. Cristiano is Cristiano, he has been this player all his life, scoring 50 goals a season.
"True, nobody else does that. But others can score, have done recently, and we must think about the positives."