What is the oxidation number for Zinc in Zn(OH)4^2-

I am trying to figure out which half reaction is the oxidation reaction and which is the reduction reaction in the redox reaction NO3^-+Zn=NH3+Zn(OH)4^2- .

Zn(OH)4= ; -2 = -4 + ?, Zn = +2 , the -4 is the charge on the 4 OH- ions.

NO3- + 6 H2O + 8 e- -------> NH3 + 9 OH-
( Zn + 4 OH- ----> Zh(OH)4= + 2e-) x 4
7 OH- + NO3- + 4 Zn + 6 H2O -------> NH3 + 4 Zn(OH)4=