Opus lets you assign a comment to a Zip file that is stored within the Zip data structure itself. In Opus you can see this comment by turning on the Description column in the file display - other Zip software will display it differently (for example, some programs will pop up a dialog showing the comment when you open the Zip file).
To edit the Zip comment, navigate into the Zip file itself, then right-click on an empty area of the file display (or on the status bar) to show the Lister Zip Context Menu, and choose the ZIP Comment command.
