Basically, this takes the original scientist zombie model and adds two submodels. The barney and soldier zombies from Opposing Force. These can be used in your map by making a monster_zombie entity, and then editing the properties in SmartEdit to add a body value. These values are:
0 = Original scientist
1 = Barney
2 = Soldier
Enjoy, and please credit UrbaNebula and probably Gearbox as well if you make use of it.