Preheat the oven to 375°F (190°C). Grease a 9×13-inch baking dish with nonstick spray and 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.
On a small plate combine the Italian breadcrumbs with 1/4 cup of the grated Parmesan. Place the flour on a separate plate and whisk the egg with 1 tablespoon water in a bowl.
Dredge each chicken tender in flour, shaking off excess, then dip in the egg wash and finally coat evenly with the breadcrumb-Parmesan mixture. Set aside.
Heat a large skillet over medium heat and add the olive oil and butter. When the butter has melted, add the breaded chicken and cook until golden brown and cooked through, about 3–4 minutes per side. Transfer to a plate 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 until saucy and evenly coated.
Spoon half of the sauced ziti into the prepared baking dish. Top with half of the diced chicken and sprinkle with half of the shredded mozzarella.
Layer the remaining pasta and sauce over the first layer, then add the remaining chicken, remaining mozzarella, and the rest of the grated Parmesan on top.
Bake until the casserole is hot and bubbly and the cheese is melted, about 25–30 minutes. Let rest about 5 minutes before serving.