Hi,
I think this is hard to achieve once your test cases are in ZS.
My first thoughts were to use a report to identify test cases with comments. I can't do this on the Cloud version of ZS but if you're on the Server version it might still have Test Library reports (for some reason not available in the Cloud version!) and it might be possible using those - but I seriously doubt it.
Next thought was test case filters but again, these are essentially the same filters available for reports, so no joy there either.
So the only other option I can suggest is to try the API (both versions linked below).
Zephyr Scale Server API (v1)
Zephyr Scale for Jira Cloud API
Regards, Andy