Hmm, I didn't pay enough attention, thought the zip was the mod. You're right in thinking the first link goes to the main download of the mod, and the zip is just a patch. The file is an .exe and from what I can tell reading the thread they made a self-extracting installer using WinZIP or WinRAR. You shouldn't need WinRAR or any unarchiver to extract it though as it should have everything it needs in the .exe.

But you could try downloading WinRAR anyway, then going to the folder with the file using WinRAR and opening it up. Any self-extracting installers made by WinZIP or WinRAR, WinRAR should be able to open and extracted manually, so maybe that could do it. I'm gonna start downloading the mod and see if I have any problems installing it but since i'm on dialup it won't be until later today before I can install and test it.

I'll let you know how it goes.