Preheat oven to 400 Degrees.
In a large saute pan fry the Zucchini until golden brown in 2-3 batches. Transfer them onto a plate lined with paper towels. Try to lightly salt them as they come out of the oil. Set aside. Reserve about 5-6 pieces to put on the very top.
Cook the Pasta half way through in salted boiling water. Drain and rinse with cold water and set aside adding a few drops of olibve oil to prevent them from sticking to each other.
In a small sauce pan add the flour to the butter once it's melted until it begins to brown. Add the milk whisking until the mixture thickens. Add Salt to taste and Nutmeg.
To assemble the Pasta al Forno, spread a thin layer of the Bechamel on the bottom of a 12 x 9 1/2 inch baking pan and add about half the pasta.
Arrange a layer of the fried Zucchini and sprinkle half the shredded Fontina and Asiago. Top with Mozzarella. Repeat the process beginning with a thin layer of Bechamel, then Zucchini, cheeses and Mozzarella. If any Bechamel remains spoon it over the top and finish with the reserved Zucchini.
Bake for 20-25 minutes or until the top has colored. You may also broil it for 1-2 minutes to get a slightly charred effect on top.