Zidane sprung a major shock before the game when he left Gareth Bale on the bench in favour of Isco, but the Frenchman explained his reasoning behind the decision.
"With Isco I looked for control of the ball and we had it, with four in the middle against three of them. Isco had a great game," Zidane is quoted by Football Espana as saying.
"We played a great team game, from the beginning. It was a well-deserved victory. We're very happy with the result and with the content of the game. We had personality, and our fans were behind the team at all times.
"Winning 3-1 isn't over. There is a return game, we have to play it and not be overconfident because it's going to be another story and we know we're going to suffer."
The return leg at the Parc des Princes takes place on Tuesday, March 6.