Preheat oven to 400°F with rack in middle position. Line pie crust with parchment paper and fill with pie weights or dried beans. Place the crust on a foil-lined baking sheet. Bake until the edges begin to set, about 12 minutes. Remove the parchment and weights and bake until lightly golden, about 5 minutes more. Let cool completely on the baking sheet on a wire rack, about 15 minutes. Reduce oven temperature to 375°F.
Using a mandoline or vegetable peeler, slice trimmed zucchini and summer squash lengthwise into long ⅛-inch-thick ribbons. Arrange the ribbons in a spiral pattern in the cooled crust.
Whisk 6 eggs, ½ cup half-and-half, pepper, ¾ teaspoon salt, ½ teaspoon garlic-herb seasoning and ½ teaspoon pepper in a medium bowl until combined. Pour the egg mixture over the vegetables. Carefully transfer to the oven, leaving the quiche on the baking sheet.
Bake until the filling is set and a knife inserted in the center comes out clean, 40 to 45 minutes.
Meanwhile, stir ⅓ cup ricotta, 1 tablespoon chives and the remaining ⅛ teaspoon each salt and garlic-herb seasoning in a small bowl until combined.
Let the quiche cool for at least 10 minutes. Dollop with the ricotta mixture. Cut into 6 wedges and serve warm or at room temperature.
