My suggestion, which may either be amplified or contradicted by some of the forum regulars, would be to invest in an ANT+ dongle and extension cable. This would allow you to connect directly to the Mac. And additional expense, but there seem to be a number of comments about BT interference.
You might also look into what is causing the Companion app to disconnect so frequently. If you are running ZC on a phone, you may want to turn off the cellular link while Zwifting and just use WiFi. (There are some threads about the cellular and WiFi competing for signal, causing ZC to lose connection when on cellular because it has to be on the same network as the Zwift app to run.
You might also change your WiFi router to run on a fixed channel instead of ‘best channel’ so that it is not regularly changing broadcast channels. The changing can also cause issues, as whatever device on which you’re running ZC gets momentarily disconnected from the network during the switch.
That’s all I’ve got, I think. Hopefully this will help, or someone else will come along with a better solution.