Zidane might reject the offer since Deschamps could leave the management of France national team after this World Cup, besides, Mbappe will leave PSG, Messi might try to leave too to Barca if possible. The team will be less competitive and will require to find substitutes for them.
Well, everything can happen. I mean, Zidane may not be interested anymore if PSG turns out to be a less competitive team. Mbappe, Neymar, Ramos, Donnarumma, or Messi has the rumor to leave PSG, I have read it several times on social media or sports news sites. If some of these key players leave PSG, surely this team becomes less competitive. But as long as the team has a plan to buy again some top players as the replacement, it won't be a big problem. The problem is when the club has no plan for new top players. If this happens, Zidane should be not interested since he knows it will be too risky for his coaching career.
In any case, the main priority for Zidane is to work as a head coach in the French national team. In principle, there are possible options, including the departure of all the above-mentioned players from the club, which is extremely unlikely, and the fact that Mbappe will remain at the club. By the way, before that there was information that, on the contrary, the arrival of Zidane as head coach may encourage Mbappe to extend his contract with Paris Saint-Germain. Also, it is likely that Antonio Conte can lead PSG, because he is not very happy with Tottenham's transfer policy and in this case a kind of castling may occur when Mauricio Pochettino may return from PSG back to Tottenham.
Rumors have it that Paris Saint-Germain are finalising the sacking of Mauricio Pochettino, which I think he deserves because he greatly underperformed with the quality of resources he had. Zinedine Zidane is the first choice and probably their best for the job but no one knows if Zidane is enthusiastic about taking the offer but for Pochettino he will likely get the job at Tottenham Hotspur. I think Conte would be let go at the end of the season and if PSG cannot get Zidane, Conte might just be considered.