Heat the extra-virgin olive oil in a large pot over medium-high heat. Once hot, add the chopped red onion and minced garlic. Sauté, stirring occasionally, until the onion becomes tender and translucent, about 5 minutes.
Add the chopped celery and coarsely diced carrots to the pot with the sautéed onions and garlic. Continue cooking for another 5 minutes, stirring occasionally, until the vegetables begin to soften.
Add the cubed sweet potato to the pot and mix all the vegetables well. Then pour in the chicken broth. Bring the mixture to a boil over high heat, then reduce the heat to low and simmer for about 15 minutes, or until the sweet potatoes and carrots are fork-tender.
Add the large pieces of zucchini to the simmering soup. Cook for an additional 5 minutes, or until the zucchini is just tender.
Stir in the herbes de Provence, salt, and black pepper to taste. Using a hand blender, carefully purée the soup in the pot until it is smooth and creamy. I like to give it an extra whirl for an ultra-velvety texture!
Add the heavy cream to the pureed soup and stir well. Purée with the hand blender one more time to fully incorporate the cream and achieve a silky finish. Serve hot and enjoy!