Using MiniZip was the obvious choice for ROL versions of RISC OS as it made zipping up an application directory extremely easy. I tried using the MiniZip file from my A9 on my Iyonix (both 32-bit computers) but the MiniZip file on my A9 appears not to work anyway.
I then looked at other compression programs. SparkFS is commercial so I can't be certain that end-users have such software. From the command line, InfoZip (v2.21beta) appears not to be able to compress an application directory. ZipEE (v1.48) does not work on the Iyonix as not 32-bit. If anyone knows of any 32-bit compression software that can compress an application directory and be controlled from the command line, please do let me know.