Why is zinc not considered a transition metal?

The electron configuration of zinc is [Ar]4s²3d¹⁰. The only oxidative state which zinc has is Zn²⁺ in which its configuration is [Ar] (4s⁰⁾3d¹⁰, as the 4s sub-level empties first. The definition of a transition metal is that it must have an incomplete d sub-level in one or more of is oxidation states. As zinc has a complete d sub level at all oxidative states it can't be considered a transition metal.