I was holding my hen and then saw 4 of these nasty things on me! I searched her neck, butt and under wing but didn't see anything. I just got her a few weeks ago and she's pretty wild so its hard to tell if she is acting different.
I don't know what pro zap garden is but I use poultry dust on mine. I apply it with a blush brush so it gets right into the skin where mites hide. A really good dusting around the vent where they hang out and a bit on her abdomen and under her wings. If your other hens have lice too you may want to do a good general clean out of the coop?
I'm talking to my vet tomorrow about using Revolution on the hens. You know those anti pest drops you can use on dogs and cats? Apparently works on chickens too so I'm going to see if I can get some. Do you want me to get back to you on what the vet says about it?
And there's a piece in the Natural Chicken Keeping thread about using things like dried lavender and dried citrus peel in the coop to discourage lice and mites.
If you give your hens access to a dust bath area, with sand, peat moss, and wood ash, they splash around and can get rid of the lice themselves that way.