In a small bowl, whisk together the Greek yogurt, Dijon mustard, hot sauce, lemon juice, and a pinch of the smoked paprika to create the remoulade; set aside in the refrigerator.
In a shallow dish, combine the remaining smoked paprika, garlic powder, onion powder, cayenne, thyme, oregano, salt, and black pepper to create the blackening seasoning.
Pat the catfish fillets completely dry with a paper towel and coat both sides generously with the prepared spice mixture, pressing it firmly into the flesh.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Place the catfish fillets in the hot skillet and sear for 3 to 4 minutes per side until a dark crust forms and the fish flakes easily with a fork.
Remove the catfish from the skillet and set aside; immediately add the sliced zucchini to the same hot pan and sauté for 3 minutes until tender-crisp and slightly browned.
Serve the blackened catfish over the sautéed zucchini and top with a generous dollop of the chilled Cajun remoulade.