I'm not sure what's going on but with both v13 and v14 of pychromecast, there are some serious degradations with the use of pyzeroconf.

home-assistant-libs/pychromecast#866
home-assistant-libs/pychromecast#897

I suggest that the assert zc.loop is not None and zc.loop.is_running() be split into two assertions since the exception does not specify which of the two conditionals failed the assertion.