Zinc is a metal that could hypothetically be smelted from sphalerite. In this version of Dwarf Fortress, however, it is not possible to smelt sphalerite by itself - it can only be smelted along with malachite in order to make brass. Strange moods may occasionally use chunks of sphalerite as secondary ingredients, resulting in artifacts decorated with zinc.
If it is somehow created (e.g. using memory hacking), zinc furniture having a background color (i.e. a door, floodgate, cage, barrel, or bin) does not render correctly - on the ground it is black, when built it is white, and while being hauled it is a semi-random color, a behavior also observed with odd artifacts such as shell cages in later versions.