Rinse and pat dry the swordfish steaks. In a bowl combine the lemon zest, herbs and pepper. Season the fish with salt and pepper. Lightly brush with mustard on one side. Press coated side into the herb mixture. In a no stick skillet heat the vegetable oil. Place fish, coated side down into the skillet and cook for 4 minutes, until the crust turns golden. Carefully turn over and cook for 3 more minutes. While fish is cooking,in a bowl toss the arugula with 1 teaspoon olive oil, season with salt and pepper,to taste. Divide greens between 2 plates. Top with the swordfish onto the arugula, drizzle with remaining olive oil.