Heat the olive oil in a large pot over medium heat. Add the onion and garlic, and cook until the onion turns soft and translucent.
Add the chicken pieces to the pot. Cook, stirring occasionally, until the chicken is lightly browned on all sides.
Stir in the zucchini slices and drained chickpeas. Cook for 2 minutes to let the vegetables start to soften.
Pour in the chicken broth and add the oregano. Bring the soup to a gentle simmer.
Let the soup cook for 15 minutes, or until the chicken is cooked through and the zucchini is tender.
Remove the pot from the heat. Stir in the lemon juice, then season with salt and black pepper to taste.
Ladle the soup into bowls and sprinkle with the chopped fresh parsley before serving.