I was thinking having both devices attached to the one set of speakers might be a bad idea, but forgot to mention it. I got sidetracked with everything else that is going on. I’d disconnect the pHat Beat speaker wires and see if you get your radio sound back.
I’m an electronic technician by trade but audio is not my area of expertise. I do know that some audio amp outputs are not tolerant of having either side grounded. If you mix and match those that could be an issue. Grounding one of the two speaker wires blows the amplifier.
What I was asking about power wise, is how its hooked up at the Pi end? I don’t see the white USB power cord plugged into anything? If your feeding power in via the GPIO pins, or soldering the wires on the bottom side of the Pi zero, you don’t need that breakout or USB cable with one end cut off. Just run two wires right from the power supply to the Pi. I have several Pi projects where I feed power in via the GPIO +5V pin 2 or pin 4 and ground to pin 6.
The amplifier had died in that speaker set after many years of service. It was just sitting there waiting to be repurposed. I mounted my pHat Beat to a Ninja diffuser. Then mounted that where the sub woofer used to be. The pHat Beat VU meter is viewable through the speaker cloth. It looks like it was meant to be there. Not liking those tiny buttons on the pHat Beat, and not being able to get at them now anyway, I added my own easy to use buttons. I have since put some labels on some of the buttons. I scored one of those picade clear with white text label sheets. That got me my volume up down, and power etc. I know which button is which but my wife wouldn’t have a clue how to turn it off if I say fell asleep listening to it lol. My electronics was in one of the side speakers. I just striped that out and covered up the holes where the volume control etc was with black electrical tape. I have some stickers on there now, but I’m thinking of going back to the black tape.