I don't think there is an endpoint to manage attachments. There is a suggestion in the roadmap portal that you can vote for, to have this type of function in the future:
Attachment management using APIs - Zephyr Scale | Product Roadmap (productboard.com)
I didn't find this poll. Is this feature already implemented?
No - you can nto access images or attachments fro support
"Additionally, Zephyr Scale Cloud currently does not offer a public endpoint to handle attachments. Images can only be added or downloaded through the UI. Unfortunately, it is not possible to add or download images via the REST API at this time. It is expected to be available within the next few quarters."
