In a bowl combine the lemon zest, dill, parsley, chervil, and black pepper. Season the fish with salt and pepper, then lightly brush with Dijon mustard on one side. Firmly press the mustard coated side of the swordfish into the lemon-herb mixture. In a skillet (preferably non-stick) heat vegetable oil. Place fish, coated side down into the hot oil. Cook for 4 minutes, until the crust turns golden. Flip and continue to cook for 3 more minutes. Meanwhile, in a bowl toss the arugula with 1 teaspoon olive oil, and season with salt and pepper, and then divide between 2 plates. Place the swordfish onto the arugula, drizzle with the remaining olive oil.