Answer is: no reaction occurs, because all salts are soluble in water.
Balanced chemical reaction:
Zn(NO₃)₂(aq) + MgSO₄(aq)→ Mg(NO₃)₂(aq) + ZnSO₄(aq).
Ionic reaction:
Zn²⁺(aq) + 2NO₃⁻(aq) + Mg²⁺(aq) + SO₄²⁻(aq) → Mg²⁺(aq) + 2NO₃⁻(aq) + Zn²⁺ + SO₄²⁻(aq).
This chemical reaction is double displacement reaction - cations and anions of the two reactants switch places and form two new compounds.
The particular reaction that represents the oxidation of Mg metal would be the following:
Mg => Mg+2 + 2e-
This is the half reaction of the oxidation of the magnesium metal, another charged species would need to receive it to become reduced or gain the 2 electrons lost.
The scientific method is defined as a method of research in which a problem is identified, relevant data is gathered, a hypothesis is formulated from this data, and the hypothesis is empirically tested.