Sauté: Heat oil in the pot over medium heat. Sauté onion, carrots, and celery for 8 minutes until softened. Stir in garlic and all spices; cook for 2 minutes until fragrant.
Simmer: Pour in broth and tomatoes. Submerge the raw chicken in the liquid. Bring to a boil, then reduce to a low simmer. Cover and cook for 25-30 minutes.
Shred: Remove chicken to a board. Let it rest for 5 minutes, then shred with forks into bite-sized chunks.
Veggies: While chicken is out, add zucchini, corn, and black beans to the pot. Simmer for 10 minutes until the zucchini is tender-crisp.
Combine: Return the shredded chicken to the pot. Turn off the heat and stir in the fresh lime juice and cilantro.
Serve: Ladle into bowls. Top with avocado slices and optional tortilla strips.