You could also split the wires coming out of the transformer (a T-tap of the proper size and using the right gauge wire works well for this), so that you now have 4 wires from the transformer and attach one set to fixed 1 and the other set to fixed 2. Obviously, the power to each track is now reduced, but it may be enough depending on the size of your layout.
You could also pick up a Z-4000 and hook up one handle to fixed 1 and the other to fixed 2 !