To add to this, I was using the v1.0.0 (latest) RZX driver for Yosemite.
I upgraded to El Capitan, installed the latest 2.0.0 driver for that OS, and still have the same issue.
I plugged in my Audio 10, hooked up the RZX to it from the master output, and my other software sees and hears the RZX through the A10.