It's already been illegal under Part 97 for a long time, why are they bringing this issue up yet again?
Part 97 Amateur Radio ยง97.113 Prohibited transmissions.
(4) Music using a phone emission except as specifically provided elsewhere in this section; communications intended to facilitate a criminal act; messages encoded for the purpose of obscuring their meaning, except as otherwise provided herein; obscene or indecent words or language; or false or deceptive messages, signals or identification.
And what does a Zello cell phone app have to do with ham radio? Nothing