Benzema's treble took him to 21 La Liga goals for the season, moving him to second in the scoring charts behind Lionel Messi, and gave him 30 in all competitions.
It also meant that, remarkably, the 31-year-old has now scored Real's last eight goals.
"I know what a player Benzema is, everyone knows it. The number of goals he's scoring is incredible," said Zidane. "I'm made up for him.
"What he's doing here, and the fact he's two goals away from his best-ever goals tally, says it all. Everyone can have their opinion on who is the best number nine in the world and for me it's Karim.
"He is confident, he knows you can always improve too, which is great. It doesn't surprise me what he's doing."
Zidane, though, was left puzzled by the fans' attitude towards Gareth Bale after they booed the Welshman during the victory.
Bale has been omitted by Zidane from the starting eleven in the club's last two La Liga games, starting just one of the last four, and is without a goal in six games.
He came on as substitute with 20 minutes remaining to a mixed reception, with his first few touches on the ball whistled by the Bernabeu crowd.
Zidane said he did not understand why the fans behaved like this towards him, especially as they applauded Isco, who came on the field at the same time.
Bale did have a good chance to end his barren sequence, only to chip over the bar when one-on-one with Iago Herrerin.
"He had a chance to score and it would've been great if he did, but it didn't go in. I don't want to get involved in the rest," Zidane added.
Bale did go some way to making up for that miss, though, by teeing up Benzema for his third goal.
(Reporting by Joseph Cassinelli; Editing by Ian Chadband)
