Preheat oven to 400 degrees F and spray large 9x13 baking dish with cooking spray. Add potatoes and zucchini. Set aside.
In a medium bowl, add sour cream, 1/2 cup cheese, garlic, dill, salt and pepper; stir until well combined. Pour over vegetables and gently mix with large spoon until well coated.
Cover with foil and bake for 45 minutes - 1 hour. Poke top potatoes with a fork to check if it they are soft and ready.
Remove foil, sprinkle with remaining 1 cup cheese and bake for another 10 minutes or until cheese has melted.
Serve casserole hot or warm, with a dollop of sour cream (if you wish), with salad or any meat.
Notes
Store: Refrigerate covered in a glass airtight container for up to 3 - 4 days. Do not freeze.If you would like to use Greek yogurt instead of sour cream: In a medium bowl, whisk 1 egg. Then add 1 cup Greek yogurt and 1 tablespoon cornstarch. Then add garlic, dil, salt and pepper; whisk until well combined.Older recipe with cauliflower: Recipe has been updated in 2023. Older version with cauliflower calls for 1.5 pounds each of zucchini, baby potatoes and cauliflower. No other changes.