For the dough, mix the flour, salt, butter in small pieces and the egg until a crumbly mixture is formed, stir in the ice-cold water and shape the dough into a ball. Wrap in cling film and refrigerate for at least an hour.
Sauté the zucchini slices in olive oil over a moderate heat for 6 - 8 minutes, season with salt, pepper and add the thyme. Drain in a colander and allow to cool. Preheat the oven to 180 ° C. Roll out the dough about 3 mm thick and line a greased baking sheet with it. Place the tray in the refrigerator for 15 minutes.
In the meantime, mix the eggs and yolks with the cream and milk, season with salt and pepper. Take the baking sheet out of the fridge, spread the zucchini and parmesan on the bottom and pour the cream and egg mixture on top. Bake the quiche for 40-45 minutes, remove from the oven and let cool down a little before serving.