All of these ports will now include the Contagion Arms! For the full list of the Ports for ZPS, head to the steam community thread.
inside the ZIP you got 2 folders, Materials and Models put them under the following folder (This folder will NOT exist by default!):
Steam\steamapps\common\Source SDK Base 2007\zpscustom
if that doesn't work, put them inside the zps folder. (WARNING: IT WILL OVERRIDE DEFAULT CONTENT!)
The models belongs to Monochrome LLC. I do NOT take any credit of anything. The only thing I've done is making sure it got ported over to 2007 Engine (ZPS).