Preheat the oven to 150°C.
Sweat the diced vegetables in olive oil in a casserole dish until tender.
Add herbs, garlic, tomato, wine, stock, and most of the citrus zest and juice to the dish.
Bring the liquid to a boil then lower to a gentle simmer.
Brown the lamb shanks in a separate pan with oil while seasoning with salt and pepper.
Transfer the lamb to the casserole dish, cover, and bake until tender.
Remove lamb from the dish and skim excess fat from the sauce.
Reduce the sauce by boiling if necessary and stir in the reserved citrus juice.
Serve lamb garnished with sauce, parsley, and reserved zest.