ZombieMod 4.0

I have this really wierd problem. Randomly only when i join a zombie mod/horde server my game will crash. It either wont load the server and freeze up or it will load the server i will play for a little while then the screen freezes and whatever sound was being played at the moment starts to play in ...

but if i compress the file how do the people that download it from the server decompress it?

i downloaded this map but it looks nothing like the picture, everything is grey and boring looking. And when i start the server it says something about the map exceeding the 16 mb limit, and my friends cannot download it.