Cristiano Ronaldo was subbed off against Levante.
Sergio Ramos put Real Madrid ahead on the 11th minute but Emmanuel Boateng levelled three minutes before the break.
Isco, who replaced Gareth Bale midway through the second half, then slotted home what looked to be the winner nine minutes from time.
Zidane then withdrew Ronaldo, presumably thinking that the win way already in the bag, and Marco Asensio entered the frame.
But Giampaolo Pazzini rescued a point for the relegation-threatened side with only one minute left on the clock.