To perform this conversion, you do not need complex coding skills. The community has developed GUI (Graphical User Interface) tools that make the process as simple as a drag-and-drop.

The most common tool for this task is simply known as ZSO Converter (often based on the ziso code by Max Loukianov).

How to use it:

  • Convert: Click the button. The software will decompress the ISO sectors, compress them using Zlib, and save the new .zso file.

    • You might ask, "Why not just use 7-Zip to make a .7z file?" Because emulators cannot read .7z or .rar files directly. The emulator must read the disk image live while you play. A ZSO is a "live readable" compressed format.

    Here are the top 3 reasons to use an ISO to ZSO converter:

    Do not convert if you require a bit-for-bit original ISO for verification, burning, or legal preservation.

    maxcso is the standard open-source ZSO converter.

    A simple graphical wrapper around the ZISO engine.

    You can tweak the command to prioritize file size or loading speed.

  • "Smart" Compression (Block Size): You can change the block size. Larger blocks generally compress better but require more memory to decompress. For PSP, sticking to the default is usually safest to avoid crashes.