Preheat oven to 425˚F.
Line a baking sheet with parchment paper or foil.
Toss chopped zucchini with olive oil and transfer to the prepared baking sheet.
Roast for 10 to 11 minutes, or until tender.
In the meantime, melt butter in a dutch oven or soup pot.
Add onions to the melted butter and cook for 2 to 3 minutes, or until tender.
Stir in garlic and cook for 20 seconds.
Stir in parsley, thyme leaves, salt, and pepper.
Add roasted zucchini to the dutch oven; stir and cook for a minute.
Pour in the vegetable broth and bring to a boil.
Cover the pot and reduce heat to a simmer; simmer for 5 to 7 minutes.
Remove the cover and using an immersion blender, blend the soup until creamy and smooth. You can also use a blender.
Return blended soup to the pot and stir in the heavy cream; cook for a minute or two, or until heated through.
Taste soup for salt and pepper; adjust accordingly.
Ladle soup into bowls.
Garnish with cooked bacon, croutons, and parsley.