Preheat the oven to 325°. Season the lamb with salt and pepper. In a large skillet, heat 1 tablespoon of the oil. Add the lamb and cook over moderately high heat until browned on all sides, about 8 minutes. Transfer the lamb to a plate and pour off the oil.
Add the remaining 1 tablespoon of oil to the skillet and add the onions, garlic and celery. Cook over moderate heat until browned, 12 minutes. Add the wine and port and boil until reduced to 1/3 cup, about 4 minutes. Transfer to a roasting pan and add the rosemary. Arrange the lamb shank and carrots in the pan, add 3/4 cup of water and cover with foil. Bake for 2 hours, turning the lamb and carrots once, until the lamb is very tender.
Transfer the lamb to a bowl. Transfer 2 of the carrots to a plate to reserve for the Cracked Emmer and Carrot Porridge. Transfer the 4 remaining carrots to a serving platter. Keep warm.
Strain the pan juices into a saucepan. Boil over high heat until reduced to 1/2 cup, 7 minutes. Shred the shank meat and add it to the pan juices; season with salt and pepper.
Sprinkle the herbs and lemon zest over the carrots. Surround the carrots with the lamb and sauce and serve.