Preheat over 450°F. Fill a large pot 3/4 of the way up with salted water; cover and heat to boiling on high.
Thinly slice the mushrooms. Halve the zucchini lengthwise, then thinly slice crosswise. thinly slice the tomatoes. microplane (or mince) 2 cloves of garlic.
Add the pasta to the pot of boiling water. Cook, stirring occasionally, 10 to 12 minutes. or until al dente (still slightly firm to the bite). Drain pasta, then transfer to a large baking dish.
Meanwhile, in a large pan, heat 1/2 tablespoon of olive oil on medium-high. Add the sliced mushrooms into a single even layer and cook, without stirring, 3 to 4 minutes, or until lightly browned. Add the red pepper flakes and season with salt and pepper. Transfer to a large baking dish. Wipe out the pan.
In the same pan you just wiped out, add 1/2 tablespoon of olive oil. Heat on medium-high and add the sliced zucchini. Cook, stirring occasionally 3 to 4 minutes, or until beginning to soften.
Reduce heat to medium. Add the tomatoes and minced garlic, and season with salt and pepper, and mix to combine. Cook until heated, about 30 - 60 seconds
Add the milk and stir until combined, about 30 seconds.
Transfer the mixture to the baking dish. Add the pasta, mozzarella, parmesan. Season with salt and pepper and stir to combine. Top with the breadcrumbs.
Bake the casserole 9 to 11 minutes, or until the breadcrumbs are lightly browned. Remove from the oven and serve.