In a large pot, heat a little oil over medium heat.
Add chopped onions and garlic; sauté until translucent.
Stir in diced carrots and celery; cook for 5 minutes.
Pour in chicken broth and water; bring to a boil.
Add the shredded chicken to the pot.
Stir in the lemon juice and zest.
Season with salt and pepper to taste.
Reduce heat and let simmer for 20 minutes.
Adjust seasoning if necessary.
Serve hot, garnished with fresh parsley.