i just ordered a kit from skintactix.com and several of their products contain zinc, ranging from 1% to 3%. after i ordered, they sent me an email that included the following:
People with prolonged moderate to severe acne develop systemic (bodily) zinc deficiency which actually promotes acne and slows the healing process considerably. If you are taking a multiple vitamin with 20-25mg of zinc this will correct a possible deficiency. If not, you may want to consider taking a multivitamin for 4-6 weeks or taking 30mg to 40mg of zinc supplement daily (with food to avoid stomach upset) for 4-6 weeks. DO NOT take zinc supplements if pregnant or nursing.
my acne is more mild than moderate so im not sure if a zinc deficiency applies to me. i plan on getting some zinc supplements just in case.
skintactix.com has more about zinc and also a very good summary of the biochemistry of acne.
pubmed.com has a number of zinc studies if you want to learn more. some of the studies contradict eachother so you gotta take each for what its worth. zinc is just one factor to consider but its surely worth trying.