Having always heard so much about the Zaino durability, something doesn't seem quite right with this scenario. If I understand correctly, your original Zaino application is about 5 months old, second layer is 4 months old, a third layer is 1 month old, yet you are having a problem with it possibly being "gone" in some areas. That isn't quite what I would expect from Zaino.
Is it possible that the #9 2.0 left some oils or some sort of residue that didn't allow the first application in June to bond correctly? If that were the case the following layers would have less than ideal conditions for survival. I don't happen to be a Zaino user, but your results seem to be rather uncommon from everything I have read about the product.
Charles