Heat the oil in a medium saucepan over medium heat. Add the onion, zucchini, celery, hominy, garlic, chili powder, and cumin, and cook until the onion softens, about 5 minutes. Add the chicken broth, pulled chicken, corn halves, bring to a boil, reduce the heat slightly, and simmer, uncovered, for 10 minutes. Add the green chiles, posole, tomatoes, and oregano and cook for another 5 minutes