<font color='#000000'>Clarification:
Only the Sony 5ES (no longer available in the US) is capable of doing this. The 3ES, 4ES, and 7ES have 2nd zone outputs, and the 7ES also has a 3rd zone output, but all are line-level only (with volume control), not amplified.
With the 5ES, you will sacrifice the centre channel in addition to the surround back (it uses 2 amp channels for the 3rd zone, leaving only 4 for the main room).</font>