Fun, Interesting concept though has some flaws (these are the things I noticed when playing the map and by looking through the editor).

There's an issue with how the border between navigations works.
Since they overlap, when you leave one the game lags and then since there on top of each other, zombies spawn right away, sometimes on top of you. The lag in loading the entire area also makes it hard to respond especially in the center. I'd suggest trying to make the zones not overlap and so that the zone isn't fully next to the world edge (as you can't tell when it ends). Have a safezone between them so they can't spawn on top of you (could have that end in a river to not interrupt the flow, though that would require a redesign). I ended up dying in the gas station b/c of this.

The boss could also be an issue, depending on what you wanted. Normal boss HP is 2000 - 4000 and you have it at 7200. This is even more of a problem as the weapons you get aren't great, with the best being an eaglefire or bluntforce (saw a few others but all of them are very rare, understandably). Main issue here being that IDK how doable the fight is or if someone would really want to grind that much to kill it.

Travel can be a bit annoying as there isn't too much to explore and several dead ends.
Adding more small locations scattered about might help but also IDK if they'd be found IDK if I'd of found any of the 'hidden' locations naturally as there far from a road and difficult to find, also probably intentional
Adding something at the ends of roads could also help so I know when they end (police stop, crashed car, etc) or just ending the road before the edge of the map. Not having zombie spawns so close to the edge and not having zombies so close to your spawn could also help. I first died b/c right as I moved I was surrounded by zombies w/ no weapons. Having something like fallen trees near the edge of the map might also help, so I wont be running into a dead end.

The lag is quite bad, I was getting about 30 fps so it was playable but not super enjoyable. I'd suggest lowering the amount of trees by at least a quarter and even more so in unimportant areas/areas you can't reach. I can't get to let alone see the outside of the map so those trees are pointless, same with the trees along the border. When you're in the visibility tab you can see that all the areas are red, meaning that there are too many objects there (trees count as objects). Lowering the amount of zombies in the forest might also help, especially when loading a new navigation. The zombies got there through the forest but why would they stay there? Some sure but that many?

Couple minor things like the road not touching the ground everywhere and some tree animals but other than that, not bad. This isn't meant to be negative just a way to help you improve, whether you do any of these things or not is up to you.


(P.S. made a discussion b/c it was over 1000 characters)