zinc absorption is not an on/off switch.. zinc *is* absorbed when stomach acid levels are low. not as well, but it does absorb.
Effect of Intragastric pH on the Absorption of Oral Zinc Acetate and Zinc Oxide in Young Healthy Volunteers (1995)http://pen.sagepub.com/content/19/5/393.short
The highest zinc plasma concentrations occurred with the acetate salt at a low [acid] intragastric pH, while the lowest plasma concentrations occurred with the oxide salt at a high [alkaline] intragastric pH...
Inhibition of gastric acid secretion reduces zinc absorption in man (1991).http://www.jacn.org/content/10/4/372.short
The areas under the plasma concentration curves for zinc were significantly reduced after ranitidine (p less than 0.01), but not after cimetidine administration. Gastric acid was also reduced after ranitidine, but not after cimetidine (500 mg) administration, suggesting that gastric acid secretion plays a role in the regulation of zinc absorption in man.
hypochlorhydria from short-term omeprazole treatment does not inhibit intestinal absorption of calcium, phosphorus, magnesium or zinc from food in humans. (1995)http://www.jacn.org/content/14/4/364.short
also. low magnesium can have an impact on stomach acid via inactivation of thiamine. I had forgotten about this study having mention of stomach acid, but it's an overall goodie:
The multifaceted and widespread pathology of magnesium deficiency (1999)http://www.medical-hypotheses.com/article/S0306-9877(00
"The range of pathologies associated with Mg deficiency is staggering:... deactivation (low gastric acid, behavioral disorders, etc.)..."