Hey,
I already gave my opinion about that mod when the 1.0 came out but I told you again : Congratulations on such an amazing achievement !
However, I'd like to give a feedback on the new animations implemented in TE4.
(1) There's an issue with Zverev's service waiting animation. He's walking on the baseline. Then he stands back to prepare his serve motion. See below :

Zverev walking on the baseline.

Zverev serving properly after standing back a little bit when switching from the service waiting animation to the serve animation.
(2) The speed of that serve.
I switched the game to free mode so the CPU shouldn't get any speed malus on his serve. I play against Zverev and I notice his serve is pretty slow while I set his serve skills at 100.
So I played a CPU vs CPU match where Zverev uses his serve animations and Opelka uses Isner serve animation (from TE Vanilla). Both players have 100 at serve power and consistency. Same problem : Zverev serves pretty slow, at the average of 180 kilometers per hour (112 mph) while Opelka serve the way he's supposed to serve at 205 kilometers per hour (127 mph).
Maybe it was just bad luck so I decided to run an experiment where Zverev would play against another Zverev. Same skills overall. The only thing I changed was the serve animation. I took Zverev animation for the fist Zverev and Fognini (from TE Vanilla) animation for the second Zverev. I let the CPU play like 8 matches at the US Open (best of 5).
Here are the results :
Zverev XTK served 572 times at the average of 181.2 kph (112.6 mph).
Zverev_test with Fognini serve served 521 times at the average of 202.6 kph (126 mph).
What you see below is an exemple of such a match. And what's amazing is ... there no problem with the second serve... only first serve.

Sorry it's in french here I should have switched into english...
I don't know if there's anything you can do to fix that. I don't even know if there's anything solvable here.
I did the same test with Medvedev and again, the serve is too slow.
Regards
Burned