While Real have made no official announcement, Zidane has claimed that he has committed to the La Liga outfit for the next two-and-a-half seasons.
However, with Real enduring a poor first half to the current campaign, Zidane has acknowledged that there are no guarantees that he will fulfill the terms of his deal.
According to AS, the 45-year-old said: "It is already signed. I have until 2020. I go match by match, year by year, like last year.
"I cannot look two or three years ahead because having the contract does not mean anything."
Fourth-placed Real sit 16 points adrift of leaders Barcelona in the league standings, although Zidane's team do have a game in hand.