Z1 and ZFX are used to help the initial layer of Zaino bond to the paint. ZFX also serves the purpose of speeding up the curing time of Z2/Z5. For the initial layer of Zaino you should use Z1 or ZFX other wise Sal recommends you use Z1 or ZFX every 10 layers. You will need ZFX if you want to apply more than 1 layer of Z2/Z5 on the same day. With ZFX you can apply 3 layers in one day.