Of course, if the user asked 'how can i get that file?' they can download the file individually, without software. Readily available compression software can be linked to if they want to download in bulk, which I find reasonable. If the user preferred to queue files up, you could link to a download manager instead, which in Firefox is simply a browser extension.
Zip compression was not chosen for folder archives because it is an expensive operation to perform on the fly. You're welcome to, however, compress the files manually and host the zip file on HFS.