Preheat oven to 350 degrees.
Season the veal with salt and pepper. Heat the olive oil and butter together in a large, heavy skillet and sear the veal shanks over high heat on all sides until well browned, about 10 minutes. Remove the browned veal shanks from the skillet and place them in an ovenproof casserole. To the same skillet to which you browned the veal add the diced vegetables, along with the garlic and saute them for 3 to 4 minutes.
When the vegetables have begun to cook and wilt, add the white wine and deglaze the pan. Add the two zests and juices and allow to reduce for several minutes. Then add the tomatoes and allow to boil before carefully pouring over veal shanks in the casserole.
Add the hot stock and the herbs to the casserole and braise, covered for 1 hour and 45 minutes. The veal should be fork tender, with the meat just beginning to separate from the bone when you move them from the oven. Do not remove until fork tender. After you have removed the veal from the vegetable sauce, stir in the gremolada and allow to be warmed through by the vegetable sauce. Serve veal shanks with some of the sauce spooned over the top. Cool for 10 minutes before serving.