10 lbs, 14 lbs too much weight to backpack. Too much volume, too.
I have camped in The Arizona Strip in Winter. I did not need a zero sleeping bag.
I camped on San Francisco mountain, near Flagstaff, and was glad for my 20 F sleeping bag. I camped on the North Rim, Grand Canyon in Winter and was glad for my 20 F sleeping bag.
Desert and trees for a hammock. It is against the law to harm a Sagaro cactus.
I would think, if you are going to ground-sleep in the desert, you would do well to have an OR Bug Bivy, or equivalent, to keep out somethinh poisonous that bites. Spend $ on that. Shake out your boots, shake out your clothing, before you put them on.
I can't think where you would need a 0 F sleeping bag this time of year?