I need iPod Downgrading Help!!!?

I downloaded the iPod software to downgrade my iPod and the software downloaded as a .zip file. I extracted everything to one folder and there is a folder called Firmware and a bunch of files like 022-3601-4.dmg and atuff like. The folder is already zipped and everytime I try to rename the file it just says .zip.ipsw. I'm at my wits end, this is impossible to do. Can someone please help me Renaming the file won't work.