With the tip of a paring knife, make about 25 X-shaped slits, each about 1/3 inch deep, all over the pork. Combine the citrus zests, oregano, chili powder, cumin, cinnamon, garlic, and 2 tablespoons salt in a bowl and work the ingredients together to make a paste. Rub the spice paste all over the pork and into the slits.