Sauté the vegetables: Heat the olive oil in a large pot over medium heat. Add the chopped onion and minced garlic, and sauté until the onion becomes translucent, about 3-4 minutes.

Cook the zucchini and carrots: Add the chopped zucchini and sliced carrots to the pot. Stir and cook for about 5-6 minutes, allowing the vegetables to soften slightly.

Add the broth and seasonings: Pour in the vegetable (or chicken) broth, then add the dried thyme, salt, and pepper. Bring the mixture to a boil, then reduce the heat to low, cover, and let simmer for about 15-20 minutes, or until the carrots are tender.

Blend the soup: When the vegetables are completely cooked and soft, use an immersion blender to blend the soup until it reaches a smooth consistency. If you prefer, you can also carefully transfer the soup in portions to a blender and blend until it's creamy.

Add the cream and lemon juice: Stir in the heavy cream (or coconut milk for a dairy-free option) and the lemon juice, if using. Taste and adjust the seasoning with more salt, pepper, or lemon juice as needed.

Serve and garnish: Ladle the soup into bowls and garnish with fresh herbs like parsley or basil for an extra burst of flavor. Serve hot with crusty bread or a light salad on the side.