I wouldn't have thought to use a zip tie to join balloons, but it sure does work! I did this with green balloons for Emery's Dora party to make trees for the forest, as part of the scavenger hunt. We hung lots of brown streamers from them to make trunks.
I like the picture because it give the illusion of space and of being weightless. Almost like being in a space ship. Silver Clouds, 1966 by Andy Warhol