In a large bowl, combine the flour, butter and salt. Cover and let chill in the freezer for 10 minutes until cold.
Use a pastry blender (or two forks) to cut the cold butter into the flour until the mixture resembles coarse, pebbled sand. Add the vinegar and 4 tablespoons ice water. Fold to combine until the dough is shaggy. If the dough is too dry, add an additional tablespoon of water. Dump onto a lightly floured work surface and gently knead together.
Pat the dough to a thickness of 1/2-inch and cover in plastic wrap. Let chill in the fridge for at least one hour (overnight is best).
Allow the chilled pie dough to sit at room temperature for 5 minutes. Working on a lightly floured work surface, roll the dough to a thickness about 1/8-inch. Transfer the dough to 9-inch pie dish.
Trim the excess dough, leaving about 1/2-inch overhang from pie dish. Flute, crimp, or decorate pie edges as desired. Cover with plastic wrap and let chill in the fridge for about 15 minutes while the oven preheats.
Preheat oven to 375 degrees F. Line pie with parchment paper and fill with pie weights (or dried beans). Bake for 15 minutes. Remove pie weights and parchment paper. Bake for another 10 minutes. Cool to room temperature.
PREPARE FILLING & ASSEMBLE:
Heat a large skillet over medium high heat. Add about 1 teaspoon of olive oil and swirl to coat pan. Add the zucchini and a pinch of kosher salt. Saute for 3 to 5 minutes, or until tender. Transfer to a dish. Repeat with the remaining vegetables, cooking each separately. Add additional oil to pan as necessary. Set aside.
Sprinkle half of the shredded cheese into the partially baked pie shell. Follow with cooked vegetables. Sprinkle remaining cheese on top.
In a large bowl, whisk together the eggs, milk, cream, salt, and pepper until no egg white streaks are visible. Slowly pour into filled pie shell. Bake for 40 to 42 minutes, or until the edges of the pie are golden brown and the center of the quiche no longer jiggles. If the edges of the pie are browning too fast, cover with foil, and continue to bake until the egg mixture is set.
Allow the quiche to cool before slicing. Serve warm or at room temperature.
Notes
These summer vegetables are high in moisture. It is best to cook them separately to prevent a soggy mess.
The raw vegetables will reduce in volume once cooked. You will end up with about 1 3/4 to 2 cups cooked vegetables. Alternatively, use any leftover cooked vegetables in place.
Store any leftovers chilled in the fridge. Reheat in a toaster oven, bring to room temperature, or serve chilled.