If you mean that you want to use CPYTOIMPF to add a file to a “compressed folder”, then, no, CPYTOIMPF won’t do it. A compressed folder isn’t a directory. CPYTOIMPF will simply replace the .zip file with an uncompressed streamfile.
You will need CPYTOIMPF to a separate file and then use some other zip utility to add the new streamfile to the .zip file.
Alternatively, you might be able to use the Qshell java ajar tool on the AS/400 to add the streamfile from CPYTOIMPF into the .zip file.