In a large pot, heat olive oil and sauté chopped onion.
Cut tomatoes, peppers and zucchini into small cubes, squeeze garlic and add all ingredients to the stewed onion.
Simmer on low heat for about 30 minutes. Add sugar, salt and pepper (to taste) to taste.
Dissolve the hermetic aid in a little water and add to the letcho, stir through and fill hot into preserving jars.