The Blues put in a solid display at home and go away with a 2-0 lead to take to the second leg at Spurs next week.
Lukaku, who was at the center of a storm at the weekend after an interview with an Italian outlet where he criticized manager Thomas Tuchel and hinted at wanting to go back to Inter Milan, was back in the starting line up.
Despite not scoring, he put in a strong shift for the team, and Ziyech was pleased with the Belgian's efforts.
Ziyech told Viasport: "The only thing we can do is support him and make him not think about other things, just about the game – and I think that's what we did the last couple of days.
"Like I said, that's why we're teammates, to support each other, and that's what we did.
"And I think even he was really sharp today and had a good performance."