In a large pot, heat olive oil over medium heat. Add chopped yellow onion and cook for about 5 minutes until translucent. Add minced garlic and sauté for another minute.

Pour in vegetable broth, followed by chopped zucchini, corn kernels, diced russet potato, and diced red bell pepper. Add dried thyme, smoked paprika, and red pepper flakes (if using). Stir well.

Bring to a boil, then reduce heat to low and cover. Let simmer for 15-20 minutes until potatoes are fork-tender.

Carefully remove 2 cups of chowder and set aside. Blend the remaining mixture until smooth and creamy using an immersion blender. Return reserved chowder back to the pot.

Stir in milk and optional heavy cream, mixing gently. Heat over low, ensuring it doesn't boil.

Taste and adjust seasoning with salt and pepper. Serve in bowls garnished with freshly chopped parsley and optional toppings.