Hello,
You could try doing user impersonation, if the Jira user exists in Zendesk, the comment will display the original Author, but if it does not exist, it will use the proxy user (user during installation). You could read more about how to impersonate a comment in the following documentation: https://docs.exalate.com/docs/how-to-impersonate-a-comment-in-zendesk
Place the following in your Zendesk Incoming Sync
replica.addedComments.each { it.executor = nodeHelper.getUserByEmail(it.author?.email) }
replica.changedComments.each { it.executor = nodeHelper.getUserByEmail(it.updateAuthor?.email) }
issue.comments = commentHelper.mergeComments(issue, replica, { it })
On Zendesk, we want to know which user created the ticket and which user added a comment. As is currently done on the Jira side.