Zidane is still possible to approach, but I'm not sure he would accept the project. We may need to wait until the end of the season for Bayern Munich to find a new coach, for now there are too many rumors that are unlikely to be true.
Apart from the issue of the new coach, I tend to want to discuss Bayern Munich's chances in the second leg of this season. Lazio will most likely have difficulty maintaining their winning aggregate because they are playing away match. I'm sure Tuchel will do everything to turn things around and take the lead in his home game, he has to make the most of everything he has for win the match.
If Lazio succeeds in taking advantage of Bayern Munich instability in the second leg, of course Lazio will create an unexpected surprise. But I see that Bayern Munich have managed to get through their difficult times in the Bundesliga where they have returned to winning ways. For the second leg, Bayern Munich are still very much favored because they are playing at home and also in terms of strength they are still very favorites to beat Lazio.
It's just that if Lazio plays defensively well enough then they have a chance to end the match with a draw and they will qualify for the next round. But Harry Kane will definitely work hard to score goals and bring Bayern Munich through to the next round. There must be no reason to make things difficult for Bayern Munich in the second leg because I checked that all the main players are ready to be in the starting eleven so Tuchel has a big opportunity to take advantage of the second leg to get their revenge.