Prepare the Mango Salsa: Combine diced mangos, avocado, red bell pepper, red onion, jalapeño, cilantro, lime juice, and a pinch of salt in a bowl. Mix gently, cover, and chill until ready to use.
Whisk Together Zesty Lime Mayo: In a small bowl, whisk together mayonnaise, lime juice, lime zest, chili powder, and cumin. Refrigerate until serving.
Season and Prepare Fish: Pat fish fillets dry and season both sides with salt and pepper.