Zinc ion transporter mediating zinc import from cytoplasm potentially into the endocytic compartment (PubMed:19521526). Controls zinc deposition in milk (By similarity). Zn(2+)(in) = Zn(2+)(out) Homodimer; dityrosine-linked. Homodimerization could be specific of the human protein and enhances the zinc transport efficiency. Enriched in vesicles within the basal region of epithelial cells. Homodimerization through dityrosine bonds is stimulated by oxidative stress. Belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family. SLC30A subfamily.