As Joe said, not recommended. You can, but it will eat up some power. That power will be converted to heat, which will warm up the cable, increasing the resistance, eating up more power. Eventually, you'll either reach equilibrium or burn up the cable. If you must, keep the volume low, and understand that it isn't going to sound as good as it will when you get a real speaker cable.
16 gauge zip cord works fine. 12 gauge is better, but doesn't always fit into the connectors.
