In a chemical reaction, iron is unable to displace zinc from zinc sulphate. Why?

Zinc is more reactive (Stronger) than iron (Weaker). When the Iron comes in contact with the Zinc Sulphate. Then both iron and zinc fight as both of them wants to get attached to Sulphate. But Zinc being stronger (reactive) than Iron wins the fight and hence Iron is unable to replace zinc from zinc sulphate.