a WordPress plugin that takes files, creates a Zip, and lets users download it
Make sure you have the ZipArchive php class activated. Once activated, just add the "download-link" class to any link you want it to work with, and include a "[zipItUpMenu]" shortcode to allow users to download all the items selected.
The CSS that gets added puts a checkbox over the element. The suggested display mode is block or inline-block, since it'll allow the anchor to take up the full width of what's inside it.