Bale picked up a calf problem on international duty with Wales last month and has not appeared since, while James recently returned to Colombia with the club's permission for the birth of his son.
The two have been back in training this week, but have been working alone and neither will take part in the game at Ipurua.
"They are not available," Zidane said. "They are not injured, but they are not available to play. They will link up with their national teams [next week]. They have five or six days to see if they are ready to play with their national teams or not."
And when pressed in another question, the Frenchman added: "They are not available now. They are not ready to play tomorrow. They haven't trained with the group. If they don't train with the group, they aren't available.
"They will assess whether they can play with their national teams. They have six days."
Bale has been called up by Wales for the Euro 2020 qualifiers against Azerbaijan and Hungary, while James is in Colombia's squad for the friendlies with Ecuador and Peru.
Brahim Diaz and Vinicius Junior return to the Madrid squad for Saturday's game, but Marcelo misses out after picking up a knock against Galatasaray in the Champions League on Wednesday.