Generously butter a cast iron skillet and preheat oven to 375 F.
Cut your shallots thin and place in a small bowl with the parmesan and flour.
Mix together and save for later. Peel your potatoes and slice them and your zucchini thin with a mandolin.
Layer the cast iron skillet with the thin potatoes followed by a layer of sliced zucchini. Top the layer with your shallot mixture and lightly pour a little olive oil on top. Do you layers again and top with potatoes.
Cover with foil and bake for 45 minutes. Uncover and bake an additional 15-20 minutes.
Once you have removed them from the oven; place a serving plate on top of the skillet and flip the skillet over leaving a beautiful looking potato zucchini gallete.