Prepare a bowl of ice water and set it near the stove. Bring a medium saucepan of water to a boil.
Cook the shrimp for 1-2 minutes until they’re just pink, then immediately dunk them into the ice water to stop any further cooking. Let sit for 5 minutes and drain well.
Chop the shrimp into small pieces and place them in a glass or non-reactive bowl.
Pour the lime, lemon, and orange juices over the shrimp. Stir to combine, ensuring the shrimp is fully submerged in the citrus juice. Cover and refrigerate for 30 minutes to 1 hour, or until the shrimp is opaque all the way through.
Remove from the fridge and add the shallots, jalapeño, tomatoes, avocado, and cilantro. Season generously with kosher salt and freshly cracked black pepper.
Gently mix everything to combine. Taste and adjust the seasoning if needed. If you prefer less liquid, you can drain some of the citrus juice.
Transfer to a serving bowl, garnish with fresh lemon zest, and serve immediately alongside tortilla chips.