1. Preheat the oven to 425 degrees F. Lightly butter the bottom of a roasting pan or line it with parchment paper.
2. Cut the lemon in half and rub the chicken with the juice and then with a tablespoon or so of the olive oil. Sprinkle with salt and pepper, less if using a preserved lemon.
3. Stuff the chicken with the remaining half lemon, a few cloves of the garlic and the herbs. Place the chicken breast up in the baking pan. Strew the remaining garlic, onion, potatoes, carrots and zucchini around the chicken. Rub with the remaining olive oil. Roast the chicken for 60 minutes, basting occasionally.
4. Reduce the heat to 375 degrees and roast until the juices run clear when you pierce the thigh, about 15 minutes or until the internal temperature reaches 110. Take the chicken out of the oven and let sit for about 10 minutes, if you want, putting a saucer under the legs, to raise them up a bit to allow the juices to flow down to the breast.
5. To make a gravy, place the roasting pan with everything thats left in it over a moderately hot heat. Pour about cup water into the pan to deglaze it, scraping up and incorporating into the gravy any bits and pieces that are stuck to the pan. Let it simmer for a few minutes and then pour into a bowl, skimming off the fat, to be passed at the table.
6. Transfer the chicken to a serving platter, surround with the vegetables, and sprinkle fresh herbs over the chicken to garnish.