There are various ways to create usable .ZIP files on AS/400s. One obvious way is to purchase a 3rd-party product or utility that provides a nice, clean user interface into functions on the system or into program code that implements the algorithms used for “zipping” files. I don’t have a list of providers, but I’m sure most search engines can give you a list.
If a purchase is out of the question or a fancy interface isn’t needed, then AS/400s with Qshell installed can use the Java jar (or ajar) tool to create .ZIP compatible files. For basic usage details, type “jar” on a Qshell command line. (For ajar, see the ajar – Alternative Java(TM) archive page.)
If you have difficulties with either of those, post your test command and results back here.