Pour a layer of marinara sauce at the bottom of the slow cooker to prevent sticking.
Sprinkle one-third of the uncooked whole grain ziti shells over the sauce.
Spoon half of the fat-free cottage cheese over the ziti, spreading it evenly.
Layer half of the sliced zucchini on top of the cottage cheese.
Sprinkle a pinch of black pepper and kosher salt over the layers.
Repeat the layering process: add another layer of marinara sauce, ziti, cottage cheese, zucchini, and seasonings.
For the final layer, top with the remaining ziti, the rest of the marinara sauce, then sprinkle the mozzarella cheese.
Cover the slow cooker and cook on low for 4-5 hours until the ziti is tender and the cheese is melted.
About 15 minutes before serving, sprinkle the grated parmesan cheese over the top, cover, and let it melt.