Yeah, you can not connect deCONZ/Phoscon and ZHA to the same Zigbee Coordinaor adapter.
Zigbee Coordinator adapters/dongles are serial devices that only support one connection.
Are you using deCONZ/Phoscon or the built-in native ZHA (Zigbee Home Automation) integration?
Or are you trying to migrate your ConBee II Zigbee Coordinator from deCONZ/Phoscon to ZHA?
If trying to migrate from deCONZ/Phoscon to ZHA then recommend migrate to new adapter, see:
If so then tip is to first perform a backup of Zigbee network + NVRAM inside deCONZ/Phoscon.
PS: Here is an old but probably still relevant thread that might help if having issues with backup: