i dont know, perhaps you could try another form of zinc? perhaps cut the zinc out completely for a few days and see how that works? maybe some food based zinc would be better for you? here is some great info on zinc and the food high in it.
do you eat meat? if so, consider getting some quality beef or calf's liver. that is chock full of b vitamins, minerals, vitamins, and every other nutrient. if eating it is distateful you can get it in dessicated capsule form. but the fresh meat is better.