Begin by pounding the chicken breasts gently to an even thickness. This will ensure they cook evenly.
In a shallow dish, pour the buttermilk and place the chicken breasts in it. Let them marinate for about 10 minutes.
In a separate bowl, combine the flour, salt, black pepper, paprika, garlic powder, and onion powder. Mix well.
Heat vegetable oil in a skillet or deep fryer to 350°F (175°C).
Take the chicken breasts out of the buttermilk, allowing any extra liquid to drip off. Dip each chicken breast completely in the flour mixture, ensuring it is evenly coated.
Carefully place the chicken breasts in the hot oil and fry for approximately 6-8 minutes on each side, or until they are golden brown and cooked through. Ensure the internal temperature reaches 165°F (74°C).
Once cooked, transfer the chicken breasts to a plate lined with paper towels to drain excess oil.
Toast the hamburger buns until lightly golden.
Spread mayonnaise on both halves of the buns.
Layer lettuce, tomato slices, and pickles (if desired) on the bottom bun.
Place the fried chicken breast on top of the toppings, and cover with the top bun.
Repeat the process to assemble the second sandwich.
Serve the Zaxby's chicken sandwiches immediately and enjoy!