The 32-year-old shows no sign of slowing down at club level despite not playing for Les Bleus since 2015
Benzema scored a late brace as Madrid beat Athletic 3-1, moving them level on points with Real Sociedad and Atletico atop the table.
The Frenchman took his tally to 10 goals in all competitions this season – more than any other La Liga player.
After the game Zidane was asked if Benzema was the best French striker ever and replied: “For me yes, in addition to what he does, what he shows, he has been at Real Madrid for a long time.
“More than 500 games, all the goals, his record. What he has done speaks for itself. For me he is the best, it is very clear.”
Benzema has become a Real Madrid legend but has not played for the France national team since 2015 after an incident involving his then national team-mate Mathieu Valbuena.
Still, the 32-year-old did score 27 goals in 81 caps for Les Bleus, in addition to scoring more than 250 goals during his time at Real Madrid.
“He is a more complete player now than he used to be. He is not a pure No.9, he doesn’t just think about scoring goals and that’s what I love about him,” Zidane, himself a French national team legend, added.
“He loves to combine with his team-mates and create chances for them but he also knows how to score goals and he does that when the team needs him the most like he did today. That’s what Karim is all about.”
Toni Kroos gave Madrid the lead at the Estadio Alfredo Di Stefano on Tuesday, where Athletic were reduced to 10 men in just the 13th minute following Raul Garcia’s red card.
But Ander Capa drew the visitors level and Madrid struggled to create clear-cut chances before Benzema delivered late.
Zidane admitted Madrid were below their best, feeling his side pushed too hard against 10 men.
“It is true that we suffered. When you play 11 against 10, if you interpret the game well you can have it easier, but it has been the other way around. We were too hasty,” he said.
“When they lose a player, you say, ‘I’m going to score the goal in 15 minutes’. And you have to be patient.
“After the fourth game in 10 days, there are three points and you have to be very happy.”
Madrid will look to extend their four-match winning streak when they visit Eibar on Sunday.