@Jeremyposey Follow these steps:

Copy ScriptHookV.dll and dinput8.dll from the downloaded file to the game's root folder, where GTA5.exe is located.
Install Microsoft .NET Framework 4.5.2 or higher. No need to do this step on Windows 10.
You will also need Microsoft Visual C++ Redistributable Package for Visual Studio 2013 (x64).
Create a folder named "scripts" in your game directory.
Copy and paste the zombie mod files in to it.

For script mods, the mods folder isn't necessary.