If it's frozen it should be bone dry. I make things bone or cracker dry by putting it in a sealed jar with the some amount of dessicant, like anhydrous calcium sulfate (drierite). Jasmine
of Mandela says: "For unlimited storage you need to dry down the buds to maximum and then pack them into the freezer".: If it has moisture in it, the freezing can begin to deteriorate the cell walls and the product itself. Even freezing meat will begin to deteriorate the flesh and if frozen more than once or twice, can spoil the meat only from the freezing.
Also, for storing in ziplocks or other plastic, plastic, though it seems impermeable, is in fact permeable. There is a slow exchange of gases through most plastics, esp. soft plastic.
Plastic baggies tend to get a charge attracting the trichomes in weed so carrying it around in very long in baggies degrades the product. One can notice pot baggies eventually becoming dusted or whitish. I've read that the whitening comes from the separated trichomes & fragments clinging to the bag.