Cut the lamb into 4 equal sized pieces, or as close as possible.
Add all of the ingredients to a baking dish and mix well with your hands. After mixing, arrange the pieces of lamb on top of the potatoes and zucchini so the potatoes and zucchini are flavored by the meat.
Bake at 400 F for an hour and fifteen minutes. Halfway through the cooking process, flip the meat and turn the potatoes and zucchini over. This will ensure even cooking throughout. The lamb should be pulling away from the bone when it's done, and the potatoes should be soft throughout.