Pin...was the only way when I started......and just don't see any reason for zippers...just an extra step as far as I am concerned. But, I must say, I will have to reline my leaders edges soon, they are getting bowed and the pins have a tendency to break the canvas and now it is getting thready.......

Sorry, I can't answer to the zippers. I pin my backings onto the canvas, takes about 15 minutes for a king size quilt, then I bast the batting and quilt top to the backing.