Modern custom firmware (like Ark-4 for PSP) and emulators (like PPSSPP and PCSX2) natively support ZSO. Top ISO to ZSO Converter Tools
Old but gold. Can output ZSO directly, with multithreading for large ISOs.
On Mac/Linux (Bash):
python pc/ziso.py compress input_file.iso output_file.zso iso to zso converter
Once finished, a new .zso file will appear in the same folder as your original ISO. Advanced Command Line Usage
maxcso "God of War 2.iso" --format=zso --output "God of War 2.zso"
Furthermore, the PPSSPP team has optimized ZSO to the point where there is absolutely no reason to keep raw PSP ISOs anymore unless you are burning discs. Modern custom firmware (like Ark-4 for PSP) and
Unzip the downloaded folder to your desktop.
Maxcso is a powerful, open-source command-line tool available for Windows, macOS, and Linux. It is widely considered the fastest converter available because it utilizes multiple CPU cores simultaneously. It can convert ISOs to both CSO and ZSO formats. 2. ZGCompress
You don't need to search for shady "specialized" software. The best converters are open-source and free. Here are the top recommended tools: On Mac/Linux (Bash): python pc/ziso
support to allow easy conversion of entire libraries from ISO to ZSO. ZISO Compressor for Windows
Oddly enough, the popular PPSSPP emulator can generate ZSOs for you.
Yes, the CPU has to decompress the file, but because the file is smaller, the SD card has to read less physical data. On fast storage (SSD/Flash), decompression is faster than waiting for the slow read of a huge ISO. Your games may actually load faster from ZSO than from ISO.