How to have double extruder and double Z motor on a 5-driver board?
I second the previous answer if running second Z motor in parallel, just split wires or buy adapter consisting of two females to one male, Z motor on most printers don't draw huge current (or at least in smaller less frequent intervals to give things time to cool). 

Erm I extruder with two temperature zones, hmmm buy a larger heating element, like a E3D Volcano or I believe they have an extreme version now, mine is rated for 40&nbsp;W+.

Or you could use external MOSFET with separate Arduino PID.