changing coaches will not make PSG win the Champions League. Because PSG since 2012 have tried to replace their coach with a popular coach. But none of the coaches have succeeded in making PSG win the Champions League trophy, when Laurent Blanc was PSG coach from 2013 to 2016, he managed to give 11 trophies and became the most successful PSG coach. Of the 11 trophies there is no Champions League trophy, so it's not because of a coach problem that made PSG fail to win the Champions League trophy.
I am not entirely sure. Of course just one coach would not change a lot, they need to retain Mbappe or get someone at that level. The talks have been about Salah, and truth be told they could pay for Salah for sure, they have that much money without a doubt. If they could Salah, and maybe like one scorer, that would be insane for them.
At left wing Neymar, at right win Salah, at behind striker Messi, and a decent level striker (not even like Haaland, just a good one is enough) would mean that they would be able to use Zidane to win UCL. I know it wouldn't be easy, but they will certainly be doing better under Zidane than how they did with Pochettino.
Zidane managed to win like 1-2 la liga titles, super cup of spain, 3 UCL!! cups, uefa super cup and fifa club world cup twice. I mean we are talking about "a manager change" of course but at the same time there is a good amount of difference between the two coaches. What does pochettino have? Sure a few ligue 1 titles and all but that is really not good enough, not good enough at all.
Zidane is both french, so that should help, and one of the best managers with that much little games played. Unless that was just pure luck for him, then he would be insanely well here. The difference is big enough that just one manager change could make a big difference.