I love to use Hazel, so this caught my eye. I can’t find anything that doesn’t use other tools in the command line. Would you be open to using any of those, or installing them outside of Hazel and then using them automatically within Hazel?
Meanwhile, the HappyScribe site which will do the conversion for you. Not sure if content privacy is an issue for your files. EditingTools.io is another site that does the same thing but with more options that you can specify.
I also found this old thread on the MPU forum, but those scripts don’t work for me (perhaps because I am on macOS 12.6?)