Beat the eggs in a medium bowl. Add the ricotta and parmesan and beat to combine. Add the salt, freshly ground black pepper, basil and thyme and beat to combine. Set aside.
Heat the olive oil in a 10" oven-proof stick-free skillet on medium high. When the oil is hot and begins to shimmer, add the zucchini slices. Stir so that the zucchini slices are all coated with some of the oil. Cook, stirring only occasionally (if you stir too much the zucchini won't brown), until the zucchini slices are lightly browned, about 5-6 minutes. Remove from heat. Remove zucchini slices from the pan with tongs or a slotted spoon to a bowl. Let cool for 30 seconds or so, and then stir the zucchini slices to the egg mixture.
Reheat the skillet. There should be a couple of tablespoons of oil left in the pan, if not, add some. When the oil is hot, pour the egg mixture into the pan. Do not stir it. Reduce the heat to medium. Let the egg mixture cook. Run a spatula along the edge of the frittata, separating the cooked edges from the pan. Let the egg mixture cook until the bottom is golden brown and the top is beginning to set, about 5-6 minutes.
Set the top rack 5" from the heating element in the oven. Preheat the oven broiler. Once the top of the frittata has started to set in the pan on the stove top, remove the pan from the stove and place it in the oven. With the broiler on, the door of the oven needs to be open. You can let the pan's handle stick out from the oven through the open door. Cook under the broiler until the top starts to become lightly browned, about 2 minutes.
Alternatively, instead of using the broiler, you can place a plate face-down on top of the skillet. Flip the skillet over to release the frittata on to the plate. Then slide the frittata from the plate back on to the skillet. Let cook for a couple of minutes more until the bottom side gets browned.
Slide the frittata out of the skillet onto a serving plate. Let cool for a minute or two and serve.
There are 423 calories in 1 serving of Zucchini Ricotta Frittata.