That particular bag does have 2 zippers, but it is opened flat and only zipped a few inches up the foot side like a normal bag. Just to close off some of the end, but allow a little venting as well.
If you were to look at it from the end of the hammock... it would be like a M ... the center of the M is where the hammock is lying, the legs of the M are draped over the loop of cord going around the hammock.
I could take some better photos if needed to show the setup better, its really dumb simple though.
It passed the overnight test and didn't shift or fall apart last night too. Toasty warm (too warm for me) all night, had to blast the fan to keep cool.
Please post some more pics when you get a chance. I've got some friends into car camping and just trying out the hammocks. This will be a great option for staying warm.