The correct IUPAC name of $\mathrm{Na}{}_2[\mathrm{Zn}(\mathrm{OH}){}_4]$ is

The complex ion is an anion, so the metal name takes the suffix -ate: zincate. Oxidation state: $x+4(-1)=-2$ gives $x=+2$. The cation is named without a numerical prefix: sodium tetrahydroxidozincate(II).