The Z50 Front and Rear hubs use the same size brake shoes and the brake panels are the same, except the brake lever are different sizes. The front brake lever is smaller than the rear brake lever. The maximum inside diameter is cast on the inside of the hubs. The maximum diameter of the hubs is 111mm. Please make sure the diameter is less than 111mm, before you start to work on the hubs.
Always a good idea to take photographs and take notes of all the components, before you start disassembly. Have the new parts like wheel bearings and seals on hand so you can make sure you have the correct parts available for reassembly.