Used as an "activator" for rubber vulcanization by sulfur and accelerators. As discovered in the early days of vulcanization, zinc has a beneficial effect on the reaction of the sulfur with the polyolefin. The stearate is a form of zinc that is highly soluble in the nonpolar medium of the polyolefins.
Being lipophilic, it functions as a phase transfer catalyst for the saponification of fats.
Some niche uses:
It is a component of some paints, imparting gloss. As a chief ingredient in "fanning powder", it is used by magicians performing card manipulation to decrease the friction between the cards.
Used to lubricate drum and rubber cleaning blades on copier machines.