The 19-year-old centre-back was shown a red card for his sliding challenge on Guerber that saw the latter suffer a double leg break.
The French football authorities have now taken action over the incident and suspended Zouma for 10 matches that will see him miss all action until the New Year.
"It was an unintentional accident," Sky Sports News quotes him as saying. "I went to tackle the ball but unfortunately, carried along by my own momentum, I injured Thomas Guerbert.
"I met him in the changing room. I have been shocked. I apologised to him, his family and everyone. I hope he will come back soon."
Guerbert added: "He came to see me in the changing room to apologise when I was with doctors and my family. I was reminded of this after the surgery. I told him that I was not angry, but that his tackle was unnecessary."
Saint-Etienne have decided not to appeal against the ban.