Cut chicken into bite-size pieces and season with salt and pepper. Heat 2 tbsp. olive oil in a large frying pan over medium-high heat. Add chicken and sauté until lightly browned, about 6 minutes. Remove chicken from pan, then add remaining oil, mushrooms, and onion. Cook until mushrooms are lightly browned, about 7 minutes. Add garlic and cook 2 minutes more. Using a slotted spoon, transfer mushroom mixture to a bowl and set aside.
Add wine to hot pan and use a wooden spoon to scrape browned bits off bottom. Add 1 1/2 cups broth and barley and bring to a boil; reduce heat to low, cover, and cook until most of liquid is absorbed and barley is tender, about 25 minutes.
Stir in remaining 2 cups broth, sherry, carrots, and thyme. Bring to a boil, then reduce heat to a simmer, cover, and cook 10 minutes. Return chicken and mushroom mixture to pan, add zucchini and parsley, and simmer until chicken is cooked through, about 7 minutes. Stir in parmesan and serve.
Note: Nutritional analysis is per serving.