Heat 2 tsp. olive oil in a large non-stick frying pan, squeeze sausage out of the casings into the pan, and cook until all liquid is evaporated and the sausage is nicely browned, about 10 minutes. (I browned the sausage in my favorite Green Pan (affiliate link). I like to use an old fashioned potato masher (affiliate link) to break the sausage apart.)

When the sausage is nicely browned, add it to a medium-sized soup pot with the chicken stock, canned tomatoes and juice, tomato paste, dried basil, dried oregano, and ground fennel. Let the mixture start to simmer over low heat.

While soup simmers, chop up the red bell pepper, green bell pepper, and onion. Heat the other teaspoon of olive oil in the same pan you browned the sausage in and cook the peppers and onions for a few minutes, then add to soup pot.

Let the soup simmer on low for 30-60 minutes. (Sixty minutes is best, but you can get away with a less if you're short on time.)

After soup has simmered for a while, make the zucchini noodles. Wash the zucchini and pat dry, then cut off both ends and cut a lengthwise slit going halfway through one side of the zucchini. Use a Spiralizer (affiliate link) on the thicker noodle blade (or other method for making zucchini noodles of your choice) to make thick half-noodles (Making a slit in the zucchini makes short noodles instead of one long one. You can see photos of the cut zucchini and short noodles here.)

Add noodles to the soup and simmer 20-30 minutes more, depending on how done you like the zucchini.

Season to taste with salt and fresh-ground black pepper and serve hot, with freshly-grated Parmesan to add at the table if desired.