Heat the olive oil in a large pan. Add onion and garlic and sauté for 5 minutes, turning occasionally.
Add the zucchini and cook for 3 - 4 minutes, stirring constantly, until they start to turn brown. Add the stock and marjoram and season everything with salt and pepper. Let the zucchini simmer for 10 minutes until the liquid has almost completely evaporated. Then arrange on a preheated platter, sprinkle with parsley and serve.