In my link on Zinc and Testosterone, I cover the controversial and often contradictory results relating zinc to testosterone. I don't think that anyone has any doubts that a zinc deficiency is going to be helpful to testosterone levels, but the studies just aren't there showing zinc as a testosterone booster. What about zinc and DHT (dihydrotestosterone)? Of course, DHT is the "other androgen" and is involved in many "male" function including libido. Does taking zinc raise DHT even though it has lackluster results with resepect to T?
One study on infertile men indicates that that may be the case.  In this (small) study, they split the men up into two groups: a lower T group with total testosterone < 480 ng/dl and a higher T group with testosterone > 480 ng/dl. What they found was interesting:
1. Testosterone, sperm count and DHT were increased by zinc in the under 480 ng/dl cohort.
2. Testosterone and sperm count were not increased but DHT was increased by zinc in the over 480 ng/dl cohort.
Of course, what is noticeable is that in both groups zinc increased DHT. Keep in mind, though, that this is just one small study on specific subpopulation. Also, isn't it interesting that the lower testosterone group increased in testosterone. Perhaps this explains some of the discrepancies we have seen in the testosterone-zinc studies?
Unfortunately, the situation is probably a bit more complicated than just that. One study indicates that the amount of zinc is very critical. At lower levels, 5-alpha-reductase activity is increased, which means that more testosterone would be converted to DHT and at higher levels the opposite was true.  Yet another study showed that, if you went high enough with zinc, it completely shut down 5-alpha-reductase activity.
So, as always, I very much recommend self-monitoring if your doctor will not work with you on this and - let's be honest - you will be lucky to get your physician to care about testosterone much less DHT. To test your DHT, check out these links: Reasonable Testosterone Labs and The Cheapest Lab Tests for men for some ideas. I have not used most of the labs, so do your own due diligence and am just passing along information that I have picked up on the Peak Testosteorne Forum.
Also, keep in mind that, if your DHT is low, creatine has been shown to increase DHT in one study. You can read about this in my link on the Potential Risks of Creatine. Finally, remember that raising your DHT if you already have solid levels could potentially lead to side effects such as hair loss. Again, testing and monitoring is always a great idea when using supplements. Read my link on Zinc Dangers for important cautions with regard to zinc use: more is NOT always better with zinc.
1) Systems Biology in Reproductive Medicine, 1981, 7(1):69-73, "Effect of Zinc Administration on Plasma Testosterone, Dihydrotestosterone, and Sperm Count"
2) J Steroid Biochem, 1984 Feb,20(2):651-5, "The effect of zinc on the 5 alpha-reduction of testosterone by the hyperplastic human prostate gland"
3) Br J Dermatol, 1988 Nov, 119(5):627-32, "Inhibition of 5 alpha-reductase activity in human skin by zinc and azelaic acid"