Place shredded zucchini in strainer and add 1 teaspoon of salt. Allow to sit for 15-20 minutes, then rinse. Divide into batches and squeeze to remove water. Add a pinch of nutmeg and pepper flakes, then set aside.
Place a kitchen towel on a work surface, then place an upside-down 13" x 9" sheet pan or cutting board on the towel. (This will serve as your pizza peel; the towel stabilizes the setup as you roll the dough.) Line the upside-down sheet pan with parchment paper, lightly grease the parchment paper with olive oil and place the dough on top. Stretch or roll the dough on the parchment into a 9-by-13-inch rectangle. If the dough shrinks, let it rest a few minutes before continuing.Brush the dough with olive oil and sprinkle shredded zucchini on top. Add shredded gruyére.
Remove the heated sheet pan from the oven and carefully slide the parchment with the dough onto the hot baking sheet. Cook until the cheese and the crust is golden brown, 14 to 16 minutes.
Use tongs to transfer the pizza to a cooling rack, leaving the parchment behind. Let sit for a few minutes to crisp and cool slightly before cutting and serving.