I am trying to book a *A award ticket using United Mileageplus. My tentative routing is as follows:

YYZ-LAX-SIN-CMB (destination and open jaw)

Return:

MLE-IST (Stopover)-YYZ

This has both TATL and Tranas Pac segments, and I am not sure if that would be allowed.

So is this a valid routing? Is there anything I can do to maximize my award redemption (by adding another stopover or any other means?)