Electrochemistry: describe question

A student writes the following equation for the reaction between zinc and iron(III) sulfate and believes it is balanced.

$$\ce{Zn + Fe2(SO4)3 -> ZnSO4 + FeSO4}$$

Describe how changes in oxidation number are used to show that this equation is not balanced and to deduce the correct coefficients. In your answer, use a Roman numeral to indicate the oxidation number of iron in iron(III) sulfate, identify which substance is oxidised and which is reduced in terms of electron transfer, and name the oxidising agent and the reducing agent.