Roll dough into a 12-inch circle. Fit dough into a 10-inch deep-dish pie plate. Fold edges under; flute. Line dough with foil; arrange pie weights or dried beans on foil. Bake at 425° for 12 minutes or until edges are golden. Remove weights and foil; bake an additional 2 minutes. Cool on a wire rack.
Reduce oven temperature to 375°.
Heat a large nonstick skillet over medium-high heat. Add oil to pan; swirl. Add zucchini and garlic; sprinkle with 1/4 teaspoon salt. Sauté 5 minutes or until crisp-tender. Cool slightly.
Arrange Basic Caramelized Onions over bottom of crust; top with zucchini mixture. Combine remaining 1/2 teaspoon salt, milk, flour, pepper, eggs, and cheese in a medium bowl, stirring well with a whisk. Pour milk mixture over zucchini mixture. Bake at 375° for 35 minutes or until set. Let stand 10 minutes before serving.