Heat olive oil in a large soup pot over medium heat. Sauté onions, carrots, and celery for about 5 minutes until softened.
Add garlic and thyme. Stir for 1 minute until fragrant.
Pour in the chicken broth and bring to a boil.
Stir in the orzo and let cook for 8–10 minutes, or until orzo is tender.
Add shredded chicken and stir to heat through.
Reduce heat to low and stir in the cream, lemon juice, and lemon zest. Simmer gently for 5 minutes.
Season with salt and pepper to taste.
Serve hot, garnished with chopped parsley and grated Parmesan if desired.