Shred zucchini using a food processor or grate by hand. You should have a little over 2 cups of shredded zucchini. Lay on top of paper towels, in a flat even layer, and top with more paper towels. Press the paper towels to absorb the excess water. Let sit while you prepare the beef.

Turn the Instant Pot to sauté mode. Once hot, add the ground beef. Cook until most of the pink is gone, about 2 to 3 minutes. Break up with a wood spoon as it cooks. Press cancel.

Add the salt, pepper, basil, and minced garlic and stir.

Add the shredded zucchini to the ground beef and stir to combine.

Add the mushrooms on top then the marinara sauce. Do NOT stir.

Close the lid and seal the vent. Cook on low pressure for 10 minutes. Quick/manually release the steam. Press cancel.

Remove the lid and stir to combine. Add 1 cup of the shredded mozzarella and the ricotta cheese. Stir to combine until all liquid is absorbed and the mixture has thickened.

Transfer to a baking dish (any size will do) and top with remaining shredded mozzarella. Place under the broiler for 3 to 5 minutes until the cheese is melted and bubbly.

Let rest 5 to 10 minutes before serving.