Both had dropped points by the time Zidane's men stepped on to the field to face Sociedad at the Santiago Bernabeu.
"It gives us added motivation because when you see that one of your rivals drops points," said Zidane. "It makes you even more eager to do the job and that's something we talked about.
"The most important things was to focus on ourselves and we managed to win.
"We have extended our lead. Our opponents have dropped points and we're now four points in front. There'll be difficult times ahead but we must enjoy this victory now."
As for the result in general, achieved thanks to goals from Cristiano Ronaldo, Mateo Kovacic and Alvaro Morata, Zidane lamented his team's early struggles.
"This is an important win for us. In the wake of a tough few days we're once again doing what we do best," he added.
"It was a strong all-round performance against difficult opposition. We managed to get the three points and keep a clean sheet, which was also important. It has been a good night because our nearest rivals all drew or lost.
"The idea at the start was for us to press, but I wasn't pleased because we weren't pressing in a very co-ordinated way. We improved on that in the second half. Possession isn't the be-all and end-all in football, you also need to have a cutting edge.
"What's more, we've got to be happy with having scored a goal like the one Kovacic got because we'd been working on that and that gives you strength."