The very first step is writing out the balanced equation. This way you will see the mole ratio of each component in the overall equation. Next, you have to take a look at the masses of the reactants given to you. Based upon the balanced equation you have written, which reactant is going to be completely consumed? (I.E. what chemical will be all used up and what one will be in excess?) Once you have that figured out, you can easily set up a ratio, using the balanced equation, to see how many moles of zinc sulfate you'll wind up with. Once you've figured out the number of moles, finding out the mass is simple.