Wash the potatoes, cover and boil in water for 20-25 minutes. Drain, rinse and peel. Press immediately through a potato ricer.
Dissolve yeast in 175 ml of lukewarm water. Mix 350 g flour, 1 1⁄2 tsp salt, 1 tsp sugar and nutmeg. Add yeast water, potatoes and 3 tbsp. oil to the flour mixture. Knead everything to a smooth dough. Cover the dough and let it rise in a warm place for about 45 minutes.
Peel and finely dice the onions and garlic. Clean, wash and chop the zucchini. Dice ham as well. Heat 2 tablespoons of oil in a large frying pan. Fry the onions, garlic, zucchini and ham for 6-8 minutes while turning.
Season to taste with salt and pepper. Leave to cool.
Coat the spring plate (approx. 30 cm Ø) with oil and dust with flour. Put approx. 50 g flour on a work surface. Knead the very soft yeast dough with your hands again. Pour the dough into the mould, press the rim up a little.
Cover again and leave to rise for about 30 minutes.
Mash the gorgonzola with a fork and mix with sour cream. Grate the gouda. Spread the vegetable and ham mixture on the dough. Add the sour cream mixture as a blob. Sprinkle with grated cheese. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for about 35 minutes.
Let the quiche rest for about 5 minutes. Remove from the mould and garnish with oregano.