Fill a large pot with 1 inch of water and bring to a boil, covered, over high heat. Place a steamer basket in the pot.
While the water comes to a boil, shred the zucchini or yellow squash into noodles using a handheld julienne peeler, a spiralizer tool, or even a regular vegetable peeler (if using a regular peeler, the noodles will be wide and flat versus spaghetti shaped). You should get 4 cups of noodles. When the water is boiling, steam the noodles in the basket for 3 minutes, then remove them and set them in a colander to drain off the excess liquid as they cool slightly. Place the snow peas on top of the noodles in the colander.
Place the shrimp in the steamer basket over the still-boiling water and cook for 4 to 5 minutes or until pink all the way through. The cooking time will vary with the size of the shrimp.
In a small mixing bowl, whisk together the sauce ingredients until well combined.
Place the noodles, snow peas, sauce, and shrimp in a large skillet over medium-high heat; toss gently to combine and heat through.
To serve, garnish with sesame seeds and top with the green onion and cucumber slices.