Here's why:

* Zirconium typically forms a +4 charge (Zr⁴⁺) in its compounds. It's extremely rare to find zirconium in a +2 oxidation state.

* Carbonate ions have a -2 charge (CO₃²⁻).

To form a neutral compound, the charges must balance. Since zirconium(II) is unlikely, you would need a different zirconium oxidation state to form a stable carbonate.

The most likely compound you're thinking of is zirconium(IV) carbonate, which would have the formula Zr(CO₃)₂. This formula ensures a neutral charge because the +4 charge of zirconium balances with the -4 charge from two carbonate ions.