1Preheat oven to 375*F. Quarter the zucchini lengthwise then slice into bite-sized pieces. Slice onion into thin half circles. Slice cherry tomatoes in half. Finely chop thyme. Use about 1/2 tbsp of olive oil to smear along the inside of the cast iron or oven-proof skillet so that the frittata will slide out easily.
2Peel potato and use mandolin or chef's knife to cut into super thin strips. Layer along the bottom of the pan no more than two slices deep (you may not use the entire potato). Whisk together eggs, milk, salt + pepper.
3Sauté veggies in about 1 1/2 tbsp olive oil on medium heat until the begin to soften, about 5-7 minutes. Season with salt and pepper. Layer cooked veggies on top of the potato slices in your skillet and pour your egg mixture over the top. Sprinkle with thyme and plop in your tomato slices on top.
4Bake for about 20-25 minutes until the middle is set and no longer jiggles when nudged. A knife inserted should come out clean. Let cool at least 15 minutes before serving.