Bale was not included in Madrid's squad for the trip to Anoeta, which finished 3-1 to Sociedad – Jesus Vallejo seeing red as Los Blancos slipped to a third defeat in their previous five La Liga fixtures on the road.
Zidane had refused to be drawn on comments from Bale's agent Jonathan Barnett that a transfer would be possible if a large offer were made at the end of the season.
However, Zidane confirmed Bale was able to play on Sunday, adding that he is unsure if the Wales international will feature again this season.
"Yes," Zidane told a news conference when asked if Bale had been fit to play against Sociedad.
"I do not know if he will play [against Real Betis]. We'll see next week.
"It's very clear what I've done this weekend. Now we have another game and then we will see next year. It is done."
The defeat also ended Madrid's slim hopes of securing a second-place finish in LaLiga, but one positive was the performance of Brahim Diaz.
The former Manchester City forward opened the scoring early on with a wonderful solo strike before Mikel Merino hit back, second-half goals from Joseba Zaldua and Ander Barrenetxea claiming the points for Sociedad.
And Zidane has been pleased with Diaz's progression.
"He has played well, he is a good player," Zidane said of the 19-year-old.
"He is a very interesting player, young and nothing more. We will see what we are going to do next year, but at the moment he has had minutes and he has done well."
Real Madrid are set to close the disappointing La Liga campaign against Real Sociedad on Saturday.