We report the large-scale synthesis of uniform-sized hexagonal pyramid-shaped ZOO nanocrystals by the thermolysis of Zn-oleate complex, which was prepared from the reaction of inexpensive and environmentally friendly reagents such as zinc chloride and sodium oleate. Under optimized reaction conditions, we were able to synthesize as much as 2.83 g using 300 mL of oleylamine and 90 mL (284 mmol) of oleic acid (OA) as both solvents and stabilizing surfactants. The UV-vis spectrum showed the absorption onset of 380 nm, and the photoluminescence spectrum showed a near band-edge emission at 387 nm and a broad blue-green emission band above 468 nm.