After winning the LaLiga and defending their UEFA Champions League title in a memorable 2016/17 campaign, Zidane has failed to replicate last season's success with Los Blancos.
Real are currently 17 points behind league leaders Barcelona with 15 games remaining and have only the Champions League to play for after being dumped out of the Copa Del Rey by Leganes at the quarter-final stage.
Striker Benzema has come under severe criticism for the club's recent struggles, with the France international only scoring six goals in 25 games all season.
"Everyone has to give a little bit more, Karim like everyone, me too," Zidane said ahead of their last-16 clash with Paris Saint-Germain, as quoted by AS. "Benzema is good for Wednesday, he is prepared and concentrating on what he has to do.
"Our ambitions this season are not acceptable and not respectable at this moment. This season is different, we have to accept it. I have to be behind my players' step by step, I am the boss of all of this and I try to improve them."