Heat the olive oil in a large pot over medium heat, add the onion, and cook for about 4 minutes until soft.
Stir in the garlic and cook for 30 seconds, then add the chopped zucchini and diced potato.
Pour in the vegetable broth and season with basil, thyme, salt, and black pepper.
Bring the soup to a boil, reduce the heat, cover, and simmer for 15 to 18 minutes until the vegetables are tender.
Add the fresh parsley and blend the soup until smooth, adding a little more broth if needed.
Stir in the lemon juice, then taste and adjust the herbs or seasoning.
Serve warm with a spoonful of Greek yogurt, or refrigerate and enjoy it chilled during warmer weather.