I've topped Zaino with Blitz and P21S. It looked great. I don't know what it will do to the long-term durability of the Zaino, though, because carnuba waxes contain solvents which may degrade the Zaino. I just don't know.
Of course, once you apply a carnuba topper, you'll have to wait until it wears off before applying more coats of Z. There is a theory that a subsequent Dawn wash will remove the wax but not the Zaino. Personally, I am skeptical about that theory. I think the Dawn will certainly degrade the Zaino, even if it doesn't remove it entirely. In the end, a good rule of thumb seems to be that once you apply a wax topper, you won't be able to apply more Z for another 3 months or so.
