z1 needs to be used the first time you zaino.
after that - you need to use it every 6 months or 10 coats... whichever comes first.
you can use zfx instead of z1. zfx should be used as least as often as the z1 schedule. zfx also allows you to apply up to 3 coats in a 24 hour period, quicker drying time, etc.