Heat the oven to 175 C / 350 F and line a 33 x 46 cm / 13 x 18 inch rimmed sheet pan with parchment. Spoon the cottage cheese into a fine-mesh sieve set over a bowl and let it drain while you prep. Grate the zucchini, wrap it in a clean kitchen towel and squeeze until it stops dripping.
Heat the olive oil in a 26 cm / 10-inch skillet over medium heat (I use my garage-sale cast iron). Cook the onion for 4 to 5 minutes until soft and translucent, then add the garlic for 30 seconds until fragrant. Scrape into a 4-quart / 3.8 L mixing bowl and let it cool for 5 minutes.
Add the drained cottage cheese, zucchini, eggs, oats, Parmesan, Worcestershire, oregano, paprika, salt and pepper to the bowl and stir to combine. Add the turkey and mix with your hands for about 1 minute, just until evenly combined. The mixture will feel soft and tacky but should hold a shape.
Turn the mixture onto the lined pan and shape it into a loaf about 25 x 12 cm / 10 x 5 inch and 7 cm / 2.75 inches tall. Bake for 50 minutes.
Stir the ketchup, brown sugar and vinegar together and spread the glaze over the loaf. Bake 15 minutes more, 65 minutes total, until the center reads 165 F / 74 C and the glaze is sticky and dark at the edges.
Rest the loaf on the pan for 10 minutes. Cut into 4 thick slices of about 6 cm / 2.5 inches with a serrated knife and serve.