How many zones do you want(not counting the AV area)? 1 or 2?
Second part of that question...
How is the Zone 2(or 3?) going to be powered?
By the AVR, or is the audio simply "getting there" to be handled by something else?
What are these "zones"?
Outdoor patio? Garage? Bedroom? Kitchen?
But to answer what you've said so far...
Airport Express(which I know nothing of...), as long as it has analog audio...fine. Everything for "the zones" must be analog. Analog is red/white. To clue you in on what that actually means...look at a picture of the back of the SR5007(you chose it, so we are going to use it as the example), those 4 sets of analog inputs on the left side next to the antenna(cable/Sat, DVD, Media Player and CD) are your inputs for Zone 2.
You choose either 5.1 main room and the "assignable" speaker terminals(the ones on the far right) to "self-power" the Zone 2. Or, you use the Zone 2 output(which coincidentally is right above the 4 inputs).
Using the far right speaker termianals "assigned" or the Zone 2 pre-out are both the correct answer.
Which are you going to use?