the zippers i've been using have been working out well. almost no problems at all.
just have to adjust the way you're zipping up, shouldn't be much problem when the hammock is weighted, when un-weighted simply hold a finger in front of the zipper so loose fabric can't get in there. if it does, just pull sideways on the fabric and it will come out, that ofter works better than trying to un-zip the snag, but one or the other should work. i've never gotten a snag that did any damage to the zipper or the fabric.