I Think you are no getting the point. I not mean the compressed CHD. I very now CHD is ultra compressed, but a way to compress .chd file into .rar or .zip ultra compressed. If it's impossible then must stay like this. But if i need to compressed all the mame roms and CHD's will be impossible to compress the down of GB it's a waste of time. Only i must now if chd compressed on rar or zip, will be emulated as normal, without using folders. Compatibility or not? Only i ask.