I'd want to try and edit the zombie generators and have them spawn green clones armed with SMGs or something.

The thing is though, I can't find where the file is in the folders for a reference. Help?

I took a look at the Lua. I don't see where it says what to have them generate though. I'm gonna assume that it's either hardcoded, it's in another Lua file, or someone(Tim?) is going to come in here and correct me.

The zombie generators are AEmitters, toggled on and off with Lua.

Go to the zombie generator code and change the emission.
(Be sure to uncomment green clones first tough.)

Yeah, the emitters are suprisingly completely controlled by Lua. This is only so that they can control how many zombies there are on the screen. Zombies are only spawned if the player is in the cave.

To have the generators spawn clones, just change it in the .ini, but to make them work like they do in the mission, you'll need the Lua as well.