Combine the ground turkey, breadcrumbs, egg, parsley, garlic, Italian seasoning, salt, and pepper in a bowl without overmixing.
Shape the mixture into small meatballs, using about 1 tablespoon of turkey for each one.
Heat the olive oil in a large pot, then cook the onion, carrots, and celery for about 5 minutes.
Add the broth, diced tomatoes, thyme, green beans, and zucchini, then bring the mixture to a gentle boil.
Carefully lower the meatballs into the soup, reduce the heat, and simmer for 18 to 20 minutes.
Check that the meatballs are completely cooked and the vegetables are tender.
Stir in the lemon juice, adjust the seasoning, and serve with additional parsley.
