Preheat the oven to 375°F and grease a 9x13-inch baking dish with nonstick spray.
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 small bowl.
Dredge each chicken tender in flour, shake off excess, dip in the egg mixture, then 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, cook the breaded chicken tenders 3–4 minutes per side until golden brown and cooked through.
Remove the chicken to a plate to 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 the 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 shredded mozzarella.
Add the remaining ziti, then the remaining chicken, then remaining mozzarella, and finally sprinkle the rest of the grated Parmesan on top.
Bake until hot and bubbly, about 25–30 minutes. Let rest about 5 minutes before serving.
