if he wins the tournament he will return to third place in the atp ranking.
if he manages to get good results in slam tournaments this year, he can start thinking about the first place overall!
Isner is playing really well at the moment. He is almost untouchable at first serve and he is making over 70% first serves. On the other hand Zverev knows how to play against him, they played 3 times and Zverev won all 3. I am thinking this one goes to 3 sets and quite possible we will see at least 2 tie breaks.
Against Isner it is going to be hard. Although Zverev has higher ATP but dont forget that Isner has made all his way to the final and he is not just going to lose the game like that. It will be a complete turnover if Isner can win the game as every sportsbook now give Isner higher odds to encourage more people to wager for him