Marinate the fish by whisking together olive oil, chili powder, cumin, smoked paprika, garlic powder, lime zest, lime juice, salt, and pepper in a bowl. Coat the fish fillets and let marinate for 15-20 minutes.

Prepare the slaw by combining green cabbage, red cabbage, grated carrot, cilantro, lime juice, olive oil, and salt in a bowl. Toss well and set aside.

Make the cilantro crema by mixing sour cream or Greek yogurt, mayonnaise, cilantro, lime juice, minced garlic, salt, and pepper in a small bowl until smooth. Chill in the refrigerator.

Cook the fish in a non-stick skillet over medium-high heat for 2-3 minutes per side until golden brown and flaky. Remove from heat and flake into large chunks.

Assemble tacos by warming tortillas, adding slaw, fish pieces, avocado, and cilantro crema. Serve with lime wedges.