@pipcat: Right now, nothing prevents you from watching something other than a PNG file, it's just that we know PNGs create a tile, making them easily user-facing (and the amount of stray OPEN/CLOSE events on those is limited)
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As for your specific idea, you cannot watch for a non-existent file with inotify (and, in kfmon's case, trying to setup a watch for a non-existent file is a fatal error that will cause the daemon to shutdown).
In this case, a simple workaround would be a wrapper script: watch for an always-there tile (i.e., a PNG), which will trigger a script which will then check for the existence of your zip file and process it if need be.
That means user-interaction, though, it won't automagically run when the zip file appears (if that was what you were trying to achieve).