trouble getting zoom audio to record in Audition

Can't say that I'm exactly surprised about that, because inherently you can't share input devices. But it would be a lot easier to determine exactly what is happening if we knew exactly how your system is configured, and what sort of mixing board we are talking about. The other thing that might help is ASIO4ALL as it's better at sharing than the native system, but we'd still need a better idea of what you're trying to achieve here.