Zinc ion transporter mediating zinc import from cytoplasm potentially into the endocytic compartment (By similarity). Controls zinc deposition in milk (By similarity). Zn(2+)(in) = Zn(2+)(out) Homodimerization could regulate efficiency for zinc transport. Enriched in vesicles within the basal region of epithelial cells. Widely expressed. Highly expressed in brain and testis. Also expressed in small intestine, medulla, lung, kidney, stomach and colon. Expressed at lower level in other tissues. Developmentally regulated in the intestine. No change in response to zinc deprivation. Belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family. SLC30A subfamily.