If you already have enough magnesium in your body, you will experience nausea and/or diarrhea. Zinc is also notorious for causing stomach upset (I assume you take it with food like you're supposed to?)
Honestly you probably aren't deficient in zinc/magnesium and are getting enough through your food. Definitely keep taking the vitamin D, you can't get that through food and unless you want the skin damage of regular sun exposure you will need to supplement D3. I would cut out the zinc/mag though.
I think that must be it. I always take it with dinner, so my biggest meal of the day. I definitely want to stay on the D3 though! I think I'll cut the magnesium and zinc! Thank you for your reply!