Heat oil with crushed red pepper and 1/2 teaspoon black pepper over medium for a 10 seconds in 8-quart heavy pot. Add chopped onion, celery, and carrots. Season with 1/2 teaspoon kosher salt. Stir in basil, thyme, dill, parsley, and bay leaf. Cook, stirring often, 10 minutes or until vegetables are softening, adding garlic for last minute or two.
Add zucchini and potatoes; stir and heat through. Pour in stock, cover, and bring to a boil. Uncover, lower heat, and simmer until vegetables are very tender -- about 15 minutes. Remove bay leaf. Using an immersion blender (or carefully in batches in food processor blender -- cover top with towel and hold firmly while processing), puree soup in pot. Taste and adjust seasonings, adding a few drops of hot sauce if desired. Stir in Parmesan and half and half; warm through. Don't boil.
To serve: add a few slices of cherry tomatoes to each bowl; ladle soup over tomatoes. Garnish with reserved basil. Serve hot or cool and chill thoroughly to serve cold over tomatoes with basil garnish. (Adjust seasonings once more for cold soup before serving.)