Add 1/3 the oil to the Wok. Add in Sausage and 1/5th of the onion. Sear and blacken slightly, drain and set aside. Add rest of oil and potatoes. Wok (stir) vigorously, allowing potatoes to rest long enough between stirs to char or blacken slightly. After 3-4 minutes when potatoes are beginning to slightly brown, toss in all the rest of the ingredients, including the spices. Continue stirring, but allow occasional pauses to blacken. After 5 mins or so, when the yellow squash stars browning or becomes tender to touch, toss in the sausage. Squeeze the juice from both Lime halfs (cut side upward to your palm so no seeds fall into the hash) into the wok. Wok for 2 mins or so. Taste one of the larger potato chunks and remove if done. Sprinkle Lime Zest all over. Serve hot!