The secret ingredient is the coffee. It gives a rich, robust depth of flavor to the sauce.
In a small bowl, combine wine, vinegar, soy sauce, coffee granules, Worcestershire sauce, and pepper. Place the steak in a large resealable plastic bag set in a shallow dish. Pour 1/4 cup of the wine mixture over the steak. Seal bag; turn to coat steak. Marinate in the refrigerator 8 to 24 hours, turning occasionally. Stir the salt into the remaining wine mixture; cover and chill until needed.
Lightly coat a grill pan with cooking spray. Heat over medium-high heat. Drain steak, discarding marinade. Cook steak on hot grill pan 10 to 12 minutes or until desired doneness (145 degrees F for medium-rare), turning once halfway through cooking time. Transfer steak to a cutting board. Let stand 3 minutes; thinly slice steak.
Meanwhile, in a small saucepan, heat the reserved wine mixture to boiling over medium-high heat. Boil, uncovered, 2 to 3 minutes or until mixture is reduced to 1/4 cup. (Or, for a more concentrated sauce, reduce mixture to 2 Tablespoons.) Spoon wine mixture over sliced steak. If desired, serve with zucchini and/or sprinkle with oregano.