1. Using either a knife, julienne slices, mandolin slicer, or spiralizer (I used a mandolin) cut the zucchini into noodle shapes…large or small, either will work.
2. In a large saucepan, heat half the oil over medium heat. Add the zucchini noodles and cook until just softened and slightly translucent. Remove to the side.
3. Add the remaining oil and heat it through, then crumble in the ground beef and add the onion and mushrooms and cook until the meat is cooked through and the vegetables are soft. Add the garlic and cook for about another minute.
4. Add the marinara sauce and season the mixture with the Italian seasoning and pepper, and salt if you desire it. Bring to a simmer, then add the zucchini back in. Note, if a lot of water accumulated in the bowl the zucchini were in, do not add it to the sauce because it will make it watery. Add the olives and balsamic vinegar as well. Toss the zucchini with the sauce, simmer for a few minutes more, then serve.