You can't directly connect via zigbee from RTI to C4, and can't get feedback, but C4 does have a means to respond to a set of IR commands, if you just want one way control of lights/the music server etc. So unless you're needing 2-way for something unrelated to the C4 parts in this system you may as well be using 433 RTI gear.

Here's the tech bulletin about all this: [Link: christyerman.customer.netspace.net.au]