Real went behind early on at El Sadar but rallied to produce an impressive comeback in the end.
"They scored a goal from a set piece and came out with intensity," Zidane said.
"There was a tough moment, 10 minutes of difficulty, but then the end of the first half and the second half were much better.
"It was very important to get back into the game quickly; it gave us confidence to play after."
Isco played a key part in the comeback, scoring the equaliser to give Los Blancos some momentum, so is the Spaniard back to his best?
"I don't know if he's at his best because he's very good," Zidane said of the midfielder.
"Having him in between the lines is very important for us. I'm happy for his goal.
"I like him a lot and technically he's important for us. I insist that I'm happy for his goal because he [still] has to do more."
Luka Jovic also found the net with a rare goal, scoring Real Madrid's fourth in stoppage time.
"I'm happy for him, he needed it too," Zidane said of the Serbian.
"He's a pure striker; you can tell him lots of things, but he's not happy if he's not scoring.
"He has to improve but I'm happy for his goal, he's going to come good."
"It wasn't the moment [for Hazard to play]," Zidane stated.
"We'll see this week; we hope to see him next week."