Peel onion and garlic and chop finely. Heat 30 grams (approximately 2 tablespoons) butter in a saucepan. Add onion and rice and cook until onion is soft, stirring constantly. Add garlic and deglaze with white wine. Ladle in about 150 ml (approximately 3/4 cup) of hot broth and cook, stirring frequently, until almost all liquid is absorbed. Continue to add broth in this manner and cook until rice is al dente, about 20 minutes, stirring frequently.
Rinse zucchini and cut into very thin slices. Heat olive oil in a non-stick pan and add zucchini slices. Cook until golden brown. Season with salt and pepper.
Stir remaining butter and half of the Parmesan into the risotto. Season with salt and pepper. Arrange the zucchini over the risotto and sprinkle with the remaining Parmesan.