How to Make It
Heat oil in a large Dutch oven over medium-high. Add next 6 ingredients; cook, stirring often, until onions are softened, about 6 minutes. Add chicken stock, rice, lime zest, and lime juice. Bring to a boil, and reduce heat to medium-low.
Cover and simmer until squash pieces are tender, about 10 minutes. Stir in chicken and chopped cilantro. Ladle into bowls; top with avocado, and, if desired, garnish with cilantro leaves.