The phrase "FIFA 21 PPSSPP ISO file highly compressed 7z extra quality" is commonly used in emulation and piracy circles. Here’s what it means:
This is typical for badly compressed FIFA mods. Try switching PPSSPP’s I/O timing method to “Host I/O” or “Fast memory” unchecked.
Crucial tip: After extraction, you should see a folder containing .ISO and .BIN or .CSO files. The ISO is usually 600MB–1GB after extraction—this is normal.