The DiscoHAT is kind of big for a PiZero. For smaller setups we have DiscoCap. It has also a 3.5mm audio out socket as this function was missing on the PiZero.
In order to keep the cost down there is no optic isolation or HAT eeprom on this board. The external push-button wires needs to be soldered directly to the holes on the DiscoCap board.