I've got 3 coats of Zaino on my windshield. Today is the third time I've driven the car in the rain. The first two times didn't cause any problems, but this time around there is a huge streak being left behind from the wiper.

Looking out of my windshield, it is being caused by the right wiper blade. When the blade makes a pass, it leaves a streak at the pinnacle of its motion. So the mark is only where the blade stops moving forward and is returning back down. Its a huge vertical streak that runs the length of the blade. You'd figure that the left blade would wipe away any residue when it makes its overlapping pass, but this is not the case.

 

Sounds like the blade is leaving a rubber residue. Try cleaning the blade with a vinyl/rubber cleaner/protectant.