Hazard left Chelsea last summer for La Liga giant, Real Madrid after leading the West London club to win the UEFA Europa League trophy.
Speaking with beIN Sports, Zola said, “They were talented players, like Hazard and Willian.
“These players know how to win matches on their own.
“But they were suffering from the type of exercises and type of training we were doing.
“I will be honest, and they were brilliant because they got bored.
“But boring is part of our job. Sometimes you need to get bored, but when you get bored you persist in what you are doing, and you get better.”