Outlaw's multichannel amps do not have an auto-sense power control: they rely on either the front power button or (more typically) the 12v trigger. The behavior that you are describing (having the main trigger remain active as long as either the main zone or the second zone is on) is intentional - your arrangement of using two channels of a seven-channel amp to drive the second zone's speakers is common, so shutting down the trigger when the main zone shut down would make it impossible to use the second zone without having the main zone on as well. Unfortunately, there is also no way to link the second zone operation to the main zone - one of the purposes for the second zone is its autonomy from the main zone.

If you wanted to leave the second zone on all the time but only listen to it when the main zone is on, you may be able to use the trigger2 to control your 7125. To do this, you would need to move the trigger cable from trigger1 to trigger2 and then change the default trigger2 setting from "off" to "on" for each input that you use (done by going to INPUT CONFIG in the 990's menu and going to each audio and video input in turn). When the 990 is off, so are all of the inputs, and trigger2 would then shut off. I say "may be able" because I don't know if having one of these zones selected for the second zone would cause trigger2 to remain active - it's very likely that it would, leaving you right back where you are now. Of course, if you are always using the same audio source for zone 2 and you never use it for the main zone, you could simply leave trigger2 set to "off" for that input. What source do you typically use with the second zone?