There feels like there's one frame missing to when her head tilts fully back.
The breast gravity is alright. And the sound is fine. Hand motions look good.
Also, I think the tag is technically more "frankenstein/promethean" rather than "zombie", though, I guess that works too.
Her loli vag is a bit lacking in detail compared to the penis. I mean, the urethra kinda has more detail xD So, need to pick up a bit in that regard. Give it some more detail to match the penis.
The sound effects really speed up near the end. Not sure if its longer than it needs to be, since its only a loop. But I guess that was for the music?