The complex ${\mathrm{K}}_4\left[\mathrm{Zn}(\mathrm{CN}{)}_4{\left({\mathrm{O}}_2\right)}_2\right]\text{ is oxidised into }{\mathrm{K}}_2\left[\mathrm{Zn}(\mathrm{CN}{)}_4{\left({\mathrm{O}}_2\right)}_2\right]$ then which of the following is/are correct? 

Oxidation state of Zn in ${\mathrm{K}}_4\left[\mathrm{Zn}{\left(\mathrm{CN}\right)}_4{\left({\mathrm{O}}_2\right)}_2\right]$ is +2 and oxidation state of Zn in ${\mathrm{K}}_2\left[\mathrm{Zn}{\left(\mathrm{CN}\right)}_4{\left({\mathrm{O}}_2\right)}_2\right]$ is also +2.  There is a peroxide linkage in ${\left[\mathrm{Zn}{\left(\mathrm{CN}\right)}_4{\left({\mathrm{O}}_2\right)}_2\right]}^{4-}$ and a dioxygen bond in ${\left[\mathrm{Zn}{\left(\mathrm{CN}\right)}_4{\left({\mathrm{O}}_2\right)}_2\right]}^{2-}$.  Bond order of peroxide is 1.5 and bond order of dioxygen bond is 2. Therefore, when product formed from reactant, then bond length of oxygen gets reduced.

As ligand in both compound is same, therefore magnetic moment of the compound remains the same.