Slice the pork tenderloin into 4 pieces. One piece at a time, cover in plastic wrap or place in a plastic bag. Using meat pounder or mallet, pound to ¼-inch thickness.
Mix together eggs, buttermilk, garlic, salt, pepper, and cayenne in a large bowl. Add pork tenderloin pieces and stir to coat each piece. Place in the refrigerator and marinate for 4-12 hours.
After at least 4 hours, remove the pork from your refrigerator and pour the buttermilk mixture into a shallow bowl. Set up another bowl with flour, and a third with the seasoned panko and cracker crumbs. Wipe excess buttermilk off of the pork pieces. Dip one piece at a time into the flour dredging both sides, then the buttermilk, and finally the seasoned panko and cracker crumbs. Press the crumbs firmly into the pork. Set each pork tenderloin piece aside on a plate or parchment for 10 minutes.
Heat ½-inches of oil in your cast iron skillet or a heavy-bottom pan over medium-high heat to 360 degrees. Working in batches of 2 at a time, pan fry your breaded pork tenderloin for 2-3 minutes on each side, until the breading is golden brown. Remove and place on a wire rack or paper towel-lined plate. Repeat these steps with your remaining pieces.