Preheat oven to 180°C. Peel onion, dice finely, sauteé in olive oil and  allow to cool down. Mix well minced meat, eggs, onion and mustard. Season with salt and pepper.
Cut zucchini into 8 parts and scoop out them, but a base be left. Fill in minced meat mixture, place them in a oiled baking dish and fry them in oven about 20 minutes.