In a large pot, heat a splash of oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.

Add the minced garlic and cook for another minute until fragrant.

Stir in the chopped zucchini and diced potato, cooking for another 5 minutes.

Pour in the vegetable broth, thyme, salt, and pepper. Bring to a boil, then reduce heat and simmer for 20 minutes until the vegetables are tender.

Using a blender, carefully blend the soup until smooth. You may need to do this in batches.

Return the blended soup to the pot and stir in the heavy cream and lemon juice. Heat through but do not boil.

Serve hot, garnished with grated Parmesan cheese if desired.