Without the injured Cristiano Ronaldo, Bale took responsibility to keep Real's title hopes alive after Rayo went 2-0 up inside 15 minutes thanks to goals from Adrian Embarba and Miku.
A towering header from Bale brought Madrid back into the game and fittingly he struck the winner nine minutes from time after Lucas Vazquez had equalised just after the break.
Bale rescues Ronaldo-less Real at Rayo
"He is very happy to make the difference," Zidane said of Bale.
"When we needed him, he was phenomenal. He scored two, but even without speaking about the goals, he played very well."
Bale's double took his tally to 18 in just 21 La Liga appearances despite an injury-disrupted campaign.
And Zidane is hopeful of more Bale magic on his first return to England since joining Madrid from Tottenham Hotspur three years ago when Real travel to face Manchester City in the first leg of their Champions League semi-final on Tuesday.
Four-star Suarez keeps Barca on top, Bale rescues Real
"I'm happy because he needed a bit of time and now he's in good shape. Now he must rest up and start thinking about Tuesday. We needed him today and he performed really well".
Madrid suffered another injury scare as Karim Benzema limped off just before half-time with a knee problem.
However, Zidane is hopeful of having both his compatriot and Ronaldo fit to face City.
"Cristiano will travel to Manchester," he added.
"We're going to assess Benzema. All that I can say is that it's not a knock. We'll get back to Valdebebas (training ground) and do what we need to do there to assess what the issue is.
"I hope that it's nothing serious and that he'll be available for Tuesday."
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