What exactly is not working? Is there a redirect but to a different destination? Or the rule is not triggering? Please keep in mind that PRs are processed in order, and only one PR triggers per URL, so you’d have to place this redirect before other generic redirects that apply to the whole zone or domain.
In your examples, is " newdomain" the same as " domain2"?
As written, you’d have a redirect to https://www.domain2.com/[number-following-mpfymap]
and not https://www.domain2.com/teacher/teacher-name/
as you apparently wants.
I now think I might not even need Cloudflare page rules to do what I want – that is to say that my main global page rule (URL forward) may be doing it’s job, and that I need to address this in the DOMAIN2 htaccess file.