"On behalf of the club, of everyone, I want to say we had a minute's silence and we are thinking of all the families of victims who were affected," Zidane said on Saturday ahead of Real's La Liga opener at Deportivo la Coruna on Sunday.
"In these very tough moments, we just want to tell them loud and clear that we are thinking of them."
Thirteen people were killed when a van ploughed into packed crowds on Barcelona's Las Ramblas on Thursday.
All games across Spain's top two divisions will be preceded by a minute's silence this weekend.
Barcelona players will also wear black armbands and shirts with 'Barcelona' replacing individual names on the back when they host Real Betis on Sunday.
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