In the bowl of a food processor or in a blender, combine the shallots with the onion and pulse until finely chopped; do NOT puree! Turn into a large bowl. Place the cucumber, fennel and hot pepper in the food processor and do the same, then add them to the onion mixture. Then add half of the tomatoes with half of the bread chunks, pulse and turn them into the bowl as well. Finally, pulse the rest of the tomatoes with the remaining bread, add them to the lot and stir to mix.
Scoop 1 cup of the vegetable mixture back into the food processor, then add the tomato juice, olive oil and vinegar and season with salt and pepper. Puree the mixture, then add it to the bowl along with the diced zucchini and bell pepper; stir to mix. Check the seasonings.
Chill the soup for at least 3 hours and up to 2 days (the longer you let it sit in the fridge, the more the flavors meld) and serve quite cold. Stir well before serving, adjust the seasonings as needed and pass the diced avocado and lime wedges on the side if desired. You may also want to give the portions a final drizzle of extra-virgin olive oil.