The speakers are connected to zone 2 speaker terminals, not the zone 2 line out. The problem is zone 2 will not accept OR output a digital signal whether you are using zone 2 powered speaker terminals or line out.Your receiver should have either zone 2 out speaker wire connections, or zone 2 line out. If you want to listen to music outside, run some speaker wire from zone 2 out on the back of the receiver to outside. Speaker wire is cheap and can be purchased almost anywhere. This would allow you to use the apple tv hdmi to onkyo receiver and get a pure digital signal. The receiver will send the music through the speaker wire to your speakers outside. Keep it simple.