Homebrew How to convert a .gcz into a .gcm or .iso for Wii emulation?

[ponyseizures]

Downloaded Fire Emblem: Path of Radiance and got a gcz file, but this won't play on the Wii. So how do I convert it?

Also, general tips on how to convert a .rar into a .iso? I unzip them and just get a bunch of .rar's inside a folder.