Place marinara sauce, water, tomato paste, Italian seasoning, and salt into an Instant Pot® and stir to combine. Add zucchini to the pot.
Place the lid on the Instant Pot® and click into place to close. Press the Pressure Cook button and adjust the timer to 2 Minutes. When the timer beeps, quick-release the pressure until float valve drops. Unlock lid.
Sprinkle mozzarella and Parmesan cheese over top. Allow 5 Minutes for cheese to melt from the residual heat. Top with sliced basil and crushed red pepper, then serve.