Zucchini, Potato, and Feta Frittata

Heat the broiler, and position an oven rack about 4 inches beneath it.
Cut the zucchini lengthwise into quarters, and slice to create wedges.
Place the potatoes in a microwave-safe bowl with 1 tablespoon of water. Cover with plastic wrap and cook on high until the potatoes are just tender, about 5 minutes. Set aside to cool, about 10 minutes.
In a mixing bowl, crack 5 of the eggs, and whisk well. Stir in the zucchini, potato, part-skim mozzarella, and about three-quarters of the feta.
Heat the oil in a 9-inch nonstick skillet. When shimmering, add the egg mixture. Cook until the edges appear set, about 5 to 8 minutes. Scatter remaining feta over the top.
Transfer to the broiler, and cook until the frittata is cooked through and browned on top, about 5 minutes more. Let stand for 5 minutes.
While the frittata is resting, fry the remaining egg and add it to the top of the frittata before serving.