You forgot to extract the 7z file. Use ZArchiver (Android) or 7-Zip (PC) to unpack the archive until you see a file ending in .iso , .bin , or .chd .
Tap the file and select "Extract Here" or "Extract to..." . aethersx2 7z
Once you have extracted your .7z to an .iso , you are ready to play. However, you can optimize further. You forgot to extract the 7z file