Total Commander will open it; I always do everything there.
What about WinRAR? Although it probably won't open it, I don't know.
There should be a "maps" folder directly inside. Look for the map there, create a ZIP archive, create a path from similar folders, and put all the files of the found map there. Then, change the extension from ZIP to MAP, and there it is, the map. But in general, look in the section and in this thread as well; there should be detailed instructions somewhere.