Grate the zucchini on a box grater or in a food processor using the shred blade.  

Remove the grated zucchini to a mesh colander over a large bowl or in the sink.  Sprinkle it with 1 teaspoon salt.  Toss well and allow the salt to pull moisture out of the zucchini for about 10 minutes.  Toss occasionally with your hands, squeezing out as much liquid as possible.

Lay a clean dishtowel on the counter and scoop the zucchini out of the colander into the towel.  Wrap the towel around the zucchini and twist and wring the zucchini to force the remainder of the water out of the zucchini.  Do this several times until you aren’t able to wring any more liquid out of the squash.

Transfer the zucchini to a large mixing bowl.

Preheat the oven to 400 degrees.  Grease a 9×13 casserole dish.  Set aside.

In a medium bowl, mix ⅔ cup sour cream, baking powder, garlic and herb seasoning, and eggs together.  Pour over the zucchini.

Add the onion, garlic, cooked rice, Parmesan cheese, mozzarella cheese, and 1 cup of cheddar cheese.  Mix well.

Pour the mixture into the prepared casserole dish.  Press down with the back of a wooden spoon to remove any air pockets and compress the casserole mixture.

Spread the remaining ⅓ cup of sour cream over the top of the casserole and sprinkle the remaining ½ cup of cheddar and the Italian blended cheeses overall.

Bake, uncovered, for 40 minutes until the casserole is set and the cheesy top is golden brown.

Allow the casserole to sit for five minutes before cutting.

Serve warm.