How to Make It
Soak the zucchini in cold water for 30 minutes. scrub them under cold running water with a brush to remove any grit. Slice off both ends and, using an apple corer, hollow out the zucchini; the aim is to scoop out their centers, leaving tubes with thin walls that will hold the meat stuffing. Be careful not to pierce the skins. Chop the scooped-out zucchini flesh rather fine and set aside.
Put 1 tablespoon of the olive oil in a large skillet and turn the heat to moderately high. When the oil is hot enough to sizzle instantly on contact with meat, add the ground veal and cook it until lightly browned, turning it a few times, about 4 minutes. use a slotted spoon to transfer it to a bowl. Do not clean out the skillet.
Put 1 tablespoon of the olive oil in the skillet. Add the garlic and cook over moderately high heat, stirring frequently, until golden, about 2 minutes. Remove the garlic with a slotted spoon and discard.
Add the chopped zucchini flesh to the skillet and brown it lightly over moderate heat, turning it from time to time, 5 to 6 minutes. Transfer the zucchini to the bowl of veal. Add the Parmigiano-Reggiano to the bowl and season with salt and pepper. Mix the ingredients to combine them uniformly. Fill the hollowed-out zucchini with the stuffing, packing it snugly.
Put the remaining 2 tablespoons of oil in a heavy 12-inch skillet and turn the heat to moderately high. As soon as the oil is hot, put in as many zucchini as will fit loosely in a single layer. Brown the zucchini on all sides, turning them as necessary; if a little bit of the stuffing falls out, it's of no consequence. Use a slotted spoon to transfer the browned zucchini to a platter. Repeat with any remaining zucchini. Do not clean out the pan.
Add the chopped onion to the pan and cook over moderately high heat, stirring, until lightly golden, about 3 minutes. Return all of the zucchini to the skillet and add the wine. While the wine bubbles away, use a wooden spoon to scrape any residues from the bottom of the pan. Sprinkle the zucchini lightly with salt. Add the tomatoes with their juices and turn over the contents of the pan once or twice. Cover, reduce the heat to low and cook for 30 to 40 minutes, gently turning the zucchini from time to time. When they are very tender and the sauce is richly flavored, remove from the heat. Let stand for about 5 minutes before serving.