Wales forward Bale has not featured for the Spanish and European champion since scoring in a 3-1 Champions League win at Borussia Dortmund in late September as a result of calf and groin injuries.
Madrid holds a 2-0 advantage over its third-tier opponent after the first leg of the round-four tie last month.
"The idea is for Bale to play, we'll see for how long," Zidane said.
"I want to see Gareth one hundred per cent as soon as possible but I cannot say when he will be like that.
"I see him in good shape to play and it is the rhythm of the match that is going to mark the way for us. We will see how much he plays tomorrow."
Zidane confirmed Croatia midfielder Mateo Kovacic is in line to play the whole game in what will be his first action since suffering a partial adductor tear against APOEL in September.
Kovacic was an unused substitute for Madrid's 3-2 win over Malaga at the weekend but all eyes are on Bale and the prospect of Zidane's famous forward line being reunited soon.
"What I want to see is Gareth, Cristiano Ronaldo and Karim Benzema all together," he added.
"It's a long time since they all played together and I'd love to see that."
Madrid captain Sergio Ramos will be absent once more due to a broken nose.