First, prepare the shrimp. If needed, thaw in the fridge overnight or in a bowl of cold water for 20-30 minutes. Pat dry thoroughly with paper towels and set in a medium-sized bowl. In a small bowl, combine all ingredients for the shrimp marinade and whisk with a fork until incorporated. Spoon atop shrimp and toss thoroughly with hands or tongs (wash hands if using). Place in refrigerator for 10-20 minutes to marinade, or up to an hour.
Next, whip up the sauce. In the bowl of a food processor, combine all ingredients for Garlic Avocado Sauce and blend until creamy and combined. Use a rubber spatula to scoop into a bowl. Cover and refrigerate until serving.
Heat 1 tbsp olive oil in a cast iron or nonstick skillet over medium heat. Once hot, add zucchini, bell pepper strips, salt and pepper to taste and saute for 5-8 minutes, tossing occasionally, until browned and soft. Remove from skillet, set in a bowl, and place aside for now.
Heat 1 tbsp more of oil in the same skillet. Add shrimp in one layer and cook for 2 minutes, then flip and cook 2 more minutes until opaque. Remove from heat and place on a plate.
To assemble: warm your favorite taco vessel in the microwave beneath a damp paper towel for about 10 seconds. Add veggies to the bottom of the taco, followed by shrimp, and finish with a generous drizzle of sauce. Garnish with feta or cotija, extra cilantro, and more lime juice, as desired.