I do not know the exact reason Zidane chose to leave Real Madrid even though until now he has not coached any team.
I think the team needs a lot of chances, starting from the president, Florentino Perez, he needs to go, along with some players that are obviously past their prime like Marcelo or Benzema.
I disagree on the part of the president because nobody can ran Real Madrid better than him in this current generation and i don't think his absence will do the team any good. The team in general needs complete overhauling together with the coaching staff, players like Karim Benzema should be sold or loaned away from the club in order to allow some young players the chance to play up there.
Ill second that no one is better than Perez to run a club like Real Madrid, Ill agree hes impatient at times but that attitude is what has delivered trophies for the club. Ill also disagree with the fact that he saw a debacle coming and left, it was due to lack of support from Perez over Bale issue which forced him to end his time at the club. I was surprised Benzema has lasted till now, half of their squad needs to be resold and they need someone like Neymar to get back their glory days.