I've done a quick search to see what I could come up with. Here goes:
In 2005, CBS Early Show featured a segment on menopause, in which the expert suggested that magnesium may be of benefit to limiting hot flashes.
In addition, I just found this article by Dr. Thomas J. Smith that was published in 2009 by the American Society of Clinical Ontology. Please note in this article that while magnesium has been suggested to help deal with hot flashes, there also can be side effects from taking too much.
I wasn't able to find anything on zinc and hot flashes.
Please note that I'm not a medical doctor, so I'd encourage you to discuss this matter with your own physician. That way you can make sure that you get what assistance you need, but don't set yourself up for any unintentional interactions with other medications, etc. that you may be taking.