Goals from Gonzalo Higuain, Angel Di Maria, Michael Essien and Luka Modric may have wrapped up a comfortable 4-0 victory over the Blanquillos but Mourinho managed to stay humble after reaching a significant milestone in his tenure.
He told AS: "I can barely believe that I've reached 100 victories.
"There were a lot of times when I applauded Zaragoza. We were tight in defence but not up front.
"There weren't that many tricky moments because we managed to stay compact.
"Maybe 3-1 would have been what Zaragoza deserved, but we produced enough chances to win.
"It didn't take much effort to control the match but we were a bit apathetic. There are times when it is difficult to stay on top.
"We have an important game against Borussia Dortmund on Tuesday.
"The team is doing well, not playing at their best, but doing well."
The visitors may have felt aggrieved at the hefty final scoreline given the fact they had held the Merengues at 2-0 for over an hour, but Essien and Modric struck at the death to flatter the hosts.
Zaragoza boss Manolo Jimenez added: "We had so many chances, we were really alive and had a great second half.
"We were no worse than Madrid on the night, it just happens to be that Madrid is one of the best teams in the world.
"We generated four clear scoring chances and (Iker) Casillas had to make three good saves, which says a lot about us.
"I know how great it feels to win at the Bernabeu, and for me, that result was not fair."