Unfortunately, zone synching is very hard. I believe that playing around with the delay settings is the best you can do on the MC end. Of course, you can do things with physical cabling that will fully synchronize zones (splitters, multi-channel amps, etc.)
The only player that I've seen do very accurate 'zone synching' out of the box is actually iTunes with their 'AirTunes' technology sending audio to the AirPort Express wireless base station.
After spending some time tuning the delays, how bad are things?
brad