Preheat the oven to 375°F (190°C) and grease a 9×13-inch baking dish with nonstick spray; set aside.
Bring a large pot of water to a rolling boil and season generously with salt.
Season the chicken tenders on both sides with kosher salt and ground black pepper.
Prepare three shallow dishes: flour in one, the whisked egg with 1 tablespoon water in the second, and Italian breadcrumbs mixed with 1/4 cup grated Parmesan in the third.
Dredge each chicken tender in flour, shake off excess, dip in the egg, then coat evenly in the breadcrumb mixture; set aside.
Heat a large skillet over medium heat and add the olive oil and butter. When the butter melts, cook the breaded chicken 3–4 minutes per side until golden brown and cooked through.
Remove the chicken from the skillet and let cool slightly, then cut into bite-sized pieces.
While the chicken cooks, add the ziti to the boiling water and cook until just under al dente. Reserve 3/4 cup of the pasta cooking water, then drain the pasta.
Return the drained pasta to the empty pot, add the marinara sauce and reserved pasta water, and stir to combine.
Spoon half of the sauced ziti into the prepared baking dish, top with half of the diced chicken and half of the mozzarella cheese.
Cover with the remaining pasta and sauce, then add the remaining chicken, remaining mozzarella, and the rest of the grated Parmesan.
Bake in the preheated oven until hot and bubbly, about 25–30 minutes. Let rest about 5 minutes before serving.