The Galacticos clinched the advantage after the first-leg of their Copa del Rey quarter-final encounter, with Marco Asensio grabbing the only goal of the game at Butarque.
And while Los Blancos now head into the return leg on January 24 with an away-goal, Zidane admits he was less than impressed with his charges on the day.
“We played a serious game and the result is very good for us,” the World Cup winner with France told Marca.
“It’s true that it cost us to find our normal play, but in the second half we were better and scored.
“We cannot say that we played a great game but we got an important result in a knockout round.”