Rinse and dry zucchini, cut off lids (set them aside).
Scrape out pulp, leaving about 1 cm (approximately 1/2 inch) shells intact.
Cut off bottoms of zucchini slightly to make zucchini stable.
Chop zucchini pulp.
Cut bacon into cubes. Peel and chop onions and garlic. Heat 2 tablespoons of oil in a pan and saute bacon, onions and garlic until soft. Add chopped zucchini pulp and chopped marjoram, season with salt, pepper, lemon juice and zest.
Stuff zucchini with the mixture and arrange in an oiled baking pan.
Replace zucchini lids and drizzle wtih olive oil. Bake in preheated oven at 180°C (approximately 350°F) for about 45 minutes. If necessary, cover zucchini with aluminum foil. Remove from the oven and serve.