Ok bro i played your map and i have to say that it needs a lot of work on it..
first you should make bigger the map because the zombie spawn is close to the humans not only that the main zombie have 50 damage and 1000 hit points. he does not need the other small skeletons :/ atleast put 2 not 4 anyway. I see what you did with the terrain when you build it, it extand more and more , you should make a refund when you build your towers outside from your buildable area. you should also make a better arena because it's too easy to walk and find the human.and one more and last thing, when a player dies you should put some special-effects and a better text warning (example : Madietor has died from the Zombie ) or something like that anyway i like your idea for such a map !!. i will rate 3/5