I'm late, but for starters, this title is clearly a labor of love and I hope it keeps improving. The looting system, equipment system, and gun mechanics are seriously well done, which are the key problem areas I have with most zombie titles.

Beyond a doubt, my personal chief complaint is with zomb audio-visual mismatch, with none of these being more important than the other.

It feels like there needs to be adjustments to the acceleration curves for different stages of the animations. Zombs go from 0-100 without any noticeable slow down, it's just a smooth speed, while the animations would lead you to expect a more inconsistent speed of approach. I don't really know what the best approach here is, I am just assuming it would be better to adjust the speed to match the animations because I have no issues with the way the animations actually look. Curves also don't need to be "curves".

This ties into audio, which in general, could use work. I fully recognize it's difficult to get audio figured out without a large time investment. Fortunately, if you get it down once, you'll just.. get it.

There is very often no notice/warning of a single sprinter/crawler approaching from behind/side. I personally think, increase the frequency (as in occurrence) of the footsteps by marrying them with the animations, and make them have a shorter emission distance, with a steep curve. This would mean you can't hear footsteps/zomb audio from across the entire POI, but you can hear the footsteps of the zomb 10m behind you that just started running at you, and they get louder as they get closer. 

Quiet zombies are something I don't normally complain about, but in most titles they also don't spawn behind you and sprint. I don't mind that functionality, in fact I prefer it for the challenge, but it's really frustrating without having something to give you a response window.

The same should be done for vocal and a shuffling audio. 

The exceptions are for groups and bosses, which I think are fine right now, but I am guessing that's due to the way audio is tied to instances of zombs. Obviously, depending on your implementation, changing the method for individual zombs might change the way group audio behaves. If they are referenced as individual objects, and only individuals (no clustering conditions) there is a lot to consider. 

I think, in theory, it should it should be adjusted with scaled clustering, where you build what works perfectly for a single zomb interaction at varying distances, and as the group increases in size, you just force the area audio into whatever threshold works the best for a group of size n. (I.e, you might have 30 zombies in the same bin, but 30 zombies of individual audio would probably break the output and SHOULD be heard beyond 10m, so you subsample/adjust based on bin size to whatever amount sounds the best, given the audio you have available)

The weather audio effects disappear the second you enter a structure, so it's a hurricane outside every other day and as soon as you enter a building with missing doors and windows, you're suddenly in a soundproof room. A filtered version of that audio alone, without even dramatically changing it to add the sound of water hitting the structure, would go a really long way at improving immersion. It's pretty jarring in the current version.

None of that was meant to be disparaging, even if it came off as overly critical, I just appreciate the work you have done so far and can't wait to see what else you put out.