You can also run out of the main LF /RF pre outs and right back into a pair of analog inputs that will never be used by the main zone so as to avoid a nasty feed back loop. then select that input for zone two playback using the internal back channel amplifiers. Which of course will only work if you are running 5.1 or less, however your zone 2 line outputs will in either case be in sync with the mains at this point.