it seems that you have a broken download, atleast that's what most of these comments are saying. I downloaded the 64 bit file and it was a empty zipped folder. it had nothing in it, might want to fix this soon.
We have looked at the download links for both x64 and x32 bit and we don't get a empty folder.
I suggest using winrar to extract the game. (We have used winrar to zip the file).
I hope this helps you with unpacking the game.