In most cases .piz files are just rename .zip files, in which case piz to zip conversion is actually not required. You just rename the suffix from piz to zip and if it's indeed ZIP you can simply extract it by right clicking on it and selecting the extract option. You actually do not have to look for some software for piz to zip conversion, although file archivers should recognize ZIP archive regardless of the file extension.
Updated: August 17, 2023