T.K.
Use a dry brush to whisk away as much of the mud as you can. Maybe even an old toothe brush to get in the cracks.
If the dry method doesn't work, you'll have no choice but to go wet. You can spray water up close or even use a medicine dropper just along the teeth, while holding a towel behind it. spray a little on and let it sit.
My last suggestion is WD-40. Again, hold a towel behind the zipper and just go along the teeth.