Zidane would have been ideal as the manager of PSG. I think the deal was unsuccessful because his focus is on becoming the next manger of the French national team if Didier Deschamps steps out which is very likely to be any time soon. Also PSG has nothing to lose. Christophe Galtier is still a good deal.
Chances will still be there and indeed it's still quite feasible how the continuation of this drama.
Galtier is doing quite well and now he has been appointed coach of PSG for next season. His cold hands this season have succeeded in bringing Nice to 5th position and troublesome for the clubs above him. Hopefully he doesn't lose his tactical skills while coaching a club as big as PSG.