The reaction of zinc with excess of aqueous alkali, evolves hydrogen gas and gives

$\mathrm{Zn}+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{ZnO}}_2+{\mathrm{H}}_2\uparrow$

In the above reaction, Zinc reacts with Sodium Hydroxide, gives Sodium Zincate with evolving of hydrogen. Here Zn does not react as an acid in the reaction above since the reaction is not an acid-base one, but rather oxidation-reduction

${\mathrm{ZnO}}_2^{2-}$ is anhydrous form of ${\left[\mathrm{Zn}{\left(\mathrm{OH}\right)}_4\right]}^{2-}$