It appears the zone 2 speakers output is in mono, "same" signal is outputed from these terminals, also the terminals are labeled A, B not L, R. as per the on-line manual in the discontinued product archives.
Swampwalker is correct. Just use your main L/R speaker outputs on the receiver to bi-wire your Missions with the appropriate cable. You may be confusing "bi-wiring" with "bi-amping". If you want to bi-amp, you'll have to find out if your receiver allows you to reassign the "back surround/zone 2" amplifier channels to play standard stereo signals instead of just the effects derived with DSP processing.
My brother-in-laws Technics SA-DA8 allows you to do this, for example. Kind of a neat feature if you think about it. A good way to take advantage of those unused amp channels in a DD/DTS receiver while listening in stereo.