Slice the ends off the zucchini and discard. Using a mandolin or carefully with a sharp knife slice the zucchini lengthwise into very thin slices. Stack the slices and cut with a knife lengthwise into 1/4 inch-thick ribbons.
Heat 1 tablespoon of the oil in large non-stick skillet over a medium heat. Add 1 clove of the garlic and cook for 30 seconds. Add the zucchini ribbons, cover and cook until the zucchini is tender, stirring occasionally, about 6 minutes. Transfer the zucchini to a bowl.
Cook the pasta al dente according to the directions on the package. Ladle out a half cup of the pasta water and set aside. Drain the pasta and return it to the pasta pot.
Meanwhile, make the sauce. Stir the flour into the low-fat milk until it is completely dissolved. Put the remaining tablespoon of olive oil in the skillet and heat over a medium-high heat. Add the remaining clove of garlic and cook for 30 seconds. Add the flour-milk mixture and cook until the mixture begins to boil, stirring constantly. Reduce heat to low and cook, stirring, for 2 minutes more. Add the evaporated milk, salt and the cheese and cook, stirring, until the cheese is melted, about 1 minute. Season with additional salt to taste.
Add the sauce, the zucchini and 3 tablespoons of the parsley to the pasta in the pot and toss to combine. Add a little of the reserved pasta water as necessary to loosen.
To serve, place 2 cups of the pasta mixture on each plate and garnish with remaining parsley.