If you want to remove zinc, or basically any other plated metal from steel use muriatic acid. It can be bought at home depot as PH down, for pools. Have some in a glass container (like a mason jar) and then dip the chunk in there with some tongs or wire. It will strip the zinc without damaging the steel. You can try it on galvanized steel wire which is everywhere if you want to see how well it works. You should only have to dip it for a few seconds. After that you can boil the part in baking soda and water for a few minutes to neutralize whatever acid is left, and then wire brush to clean them up. Make sure not to do the muriatic acid inside, as its somewhat noxious and can rust metal tools if you're in a workshop. I used to keep an orange home depot bucket outside of the forge for cleaning things so that it wouldn't rust anything inside.
It's a gloves only sort of acid, but it works so well for cleaning of zinc coatings that I always have it around. Especially if you're going to be doing welding or something, a quick dip can save you all of the zinc poisoning. Hope that helps!