Boil chicken breast in boiling water until cooked.
Remove the cooked chicken breast, let it cool, then shred it along the grain.
In a pot for broth, add water, green onion, and garlic, and bring to a boil.
Add the chicken breast to make the broth.
Add knife-cut noodles and bring to a boil.
Add zucchini, carrot, and onion and cook until tender.
Season with soy sauce and salt to taste.
Serve in a bowl and garnish with green onion.