Zverev should really work hard on his serving, I think we can all agree on that. It's a weakness right now, and with his height, he should be able to do a lot better.
It should be his main focus for improvement imho. Will come in time I believe.
In all, I think Zverev was a bit overwhelmed at the occasion, certainly during that 1st set. The lack of experience was showing, but hey, the guy is still a teeniebopper!
As for "Fed's UEs being more of the forced variety", I just have to respectfully disagree. The way he lost his serve game was just absymal from Fed!error, there wasn't as much Zverev got to do there.
We'll have to wait and see. Things can change quickly, and if I have to believe all of the press about Fed not being sure to play this morning...
In any case, I hope for the both of them to show up in good form.