Bring a pot of salted water to a boil. Add the pasta and cook until al dente. Drain the pasta and set aside.
Meanwhile, heat 2 tablespoon each olive oil and butter in a large cast iron skillet over high heat. Add the green and red bell peppers and mushrooms and sprinkle over the garlic and 2 teaspoons Cajun seasoning. Let the peppers and mushrooms sit a few seconds, so they start to blacken on the bottom, then cook, stirring gently, about 1 minute.
Add the remaining tablespoon of olive oil and butter. Throw in the zucchini, and another 2 teaspoons of Cajun seasoning and cook, stirring, for an additional 1 to 2 minutes.
Reduce the heat to medium-high. Pour in the broth and bring to a boil. Cook for 5 minutes, scraping the bottom of the pan. Reduce heat to medium-low, pour in the heavy cream followed by the tomatoes and cook, stirring constantly, until thickened, 3 minutes. The sauce should be spicy.
Add the cooked pasta, scallions to the sauce and toss to coat. Season to taste with salt and pepper. Sprinkle over chopped parsley and serve.