To a medium pot, set over medium-low heat, add the olive oil. When warmed, add the zucchini, carrots and mushrooms. Add a few pinches of salt, oregano, crushed red pepper and garlic. Cook until softened, about 10 minutes. Add the crushed tomatoes; bring to a gentle simmer and cook, partially covered, for about 10 minutes. Taste and adjust the salt to your liking. Turn the heat to low and continue cooking until you’re ready to use the sauce.