The zinc galvanization process creates an intermetallic bond between the steel and the zinc. Just removing the visible zinc layer is not sufficient, as there is still zinc in the outer layer of steel.
Zinc starts fuming as low as 200F. Zinc Fumes can make you extremely sick and the smell/taste is not one you want on food.
If you really want to use this piece of metal - take a layer of steel off after you remove all the zinc (1 mm is probably enough). Then, I would try to find a way to heat it up to 500+ degrees for a while to cause any remaining zinc to outgas. (Why 500? - the hotter it is, the faster it outgasses).
Personally, I would never use any galvanized metal in any cooking appliance, no matter how well I thought I cleaned it. it is not worth the risk to me of getting my family and/or friends sick.