Real Madrid is definitely not the same team as it was a few years ago. Remember, Real won three consecutive Champions League titles when Zidane was the head coach. I believe Xabi can motivate them and elevate the team to a higher level. They just need to stay healthy and be in top form.
Replicating what Zidane did at Real Madrid won't be easy for a new coach at Real Madrid, as it's not without reason that I say that when we refer to the quality of the players Zidane coached and the quality of the players currently at Real Madrid. Real Madrid fans certainly know and can draw a clearer comparison, because the difference between Zidane's time with Ronaldo and the current squad for a team of Real Madrid's stature is stark.What Zidane has done was once what will never happen again probably.
He got lucky on many levels and I think he knows it and that is why he doesn't return to the business because he would be measured by what he has done on the past and he knows it can't be done again.