Ok thanks, I'll look at these files :)

Well, I've modified my shotgun to test and the game crashed with the same error, so it's not your mod. And so it must be impossible to fight Zimmerman with a modified weapon.

lol, I think you did something wrong instead.

Csimbi's "armour of god" mod has the same problem. I hope I did something wrong, but I just modified shotgun damage :)

Let's be sure: remove or rename your lscripts dir -> fight zimmy. If it crashes reinstall&repatch the game.
If it works, create a new LSCRIPTS\Templates\Weapons directory and put your modified shotgun there -> fight zimmy. If it crashs PM me your shotgun.
If it works either be happy or try to diagnose the problem, for the sake of knoledge!

I did what you said. The game is not crashing when i'm fighting against him, but when I kill him before he destroy the floor (it seems to be that). It must be a Compulsory script. I'll try to kill him after he destroyed the ground.

You mean it crash even WITHOUT any mod?
Or did it crash when you had only one file in the LSCRIPTS: Shotgun.CWeapon

I don't know, I've never killed him during the first part of the fight without mod :) And with the armour of god mod, I've the same problem.

Use godmode to test in non-modded game
if you're playing in hard mode you may wish to modify lscripts\HUD\console.lua line 1161 so as to allow godmode in hard difficulty.

I can't, I play in hard mode, so cheats don't work.

edit : OK, thanks for the tips, I'll try it, but not now :)