In response to my question Michiel Beijen was kind enough to reply:

...

My agents would prefer a plain text display in the Agent Zoom View of a ticket. I have searched Defaults.pm, the documentation, and SysConfig in the admin section and cannot find out how to set this.

try Admin > SysConfig > Framework > Core::Web > Frontend::RichText if you set this to No, the rich text editor will be disabled.

Yes, that was already done. My request has to do with the viewing of the email when you select Zoom for a specific ticket. It displays that ticket in HTML format instead of plain text. We would prefer this display be in plain text (like the Overview). Is there a way to do that? Thanks. - Richard