Are you using Z1 or ZFX?
How many coats per day?
How much product per coat do you feel you have applied?
Humidity and temperature conditions?
I have found that Zaino streaks if:
1. You let the product setup properly in high humid or low temperature conditions
2. You apply the product too thick
3. You apply to many coats in one day (I usually only do 2) using ZFX. If you going the Z1 every 10 coats, then you can only apply 1 coat per day.