Peel and cook whole potatoes, covered, in lightly salted boiling water for 20 to 25 minutes or until just tender; drain, cool slightly, and thinly slice. Preheat oven to 375 degree F.
Meanwhile, for crust, stir together flour and 1/2 teaspoon of the salt; cut in butter until pieces are pea-size. Stir in 1 cup of cheese. Sprinkle 1 tablespoon of the water over part of the mixture; gently toss with a fork. Push moistened dough to side of bowl. Repeat, using 1 tablespoon of the water at a time, until all dough is moistened. Divide in half. Form each half into a ball.
On a lightly floured surface flatten 1 dough ball. Roll into a 12-inch circle. Ease pastry into a 9-inch pie plate. Arrange potatoes in pastry-lined pie plate. Sprinkle Italian seasoning and remaining 1/4 teaspoon salt over potatoes. Sprinkle with 1/4 of cheese. Sprinkle with carrot and 1/4 cup of cheese. Next sprinkle with onion and 1/4 cup of cheese.
Top with zucchini and remaining cheese. Trim pastry to edge of pie plate. Roll remaining dough into a 12-inch circle. Cut slits to allow steam to escape. Place remaining pastry on filling; trim 1/2 inch beyond edge of plate. Fold top pastry under bottom. Crimp edges.
Cover edge with foil. Bake 25 minutes. Remove foil; bake 20 to 25 minutes more or until olden. Cool 15 to 20 minutes before serving. Makes 6 servings.