When you take supplements you need them to also be absorbed to benefit from them. Unfortunately, it is not as simple as buying a mineral tablet, as many companies have not bothered looking into the bioavailability, nor how minerals compete for absorption - and thus they should NOT be taken at the same time.
Zinc and Magnesium shouldn't be taken at the same time.
Not for any bad effects, but for the simple reason of absorption. Zinc and Magnesium both fight for absorption when taken together so you should space them out.
Zinc and magnesium are best absorbed on an empty stomach, but if it messes with your stomach have it with some food.
Magnesium is best taken at night before sleep as it relaxes the muscles.
Take zinc in the morning just before breakfast and then take magnesium at night before sleeping to help with muscle soreness and recovery.
You guys out there might want to keep in mind that both magnesium and zinc are involved in healthy male sexual performance - and deficiencies are almost always seen in issues concerning erection dysfunction and premature ejaculation.
Reference: Proc Nutr Soc. 1999 Feb;58(1):147-53. The regulation of mineral absorption in the gastrointestinal tract. Powell JJ