Complex sentence: He covers up the Turtles existence by telling Joan Grody that they were just people in costumes like the Pulverizer, but even so, it doesn't mean that their punishment is over.
Split into simpler sentences: He covers up the Turtles existence by telling Joan Grody that they were just people in costumes like the Pulverizer. Even though the Turtle's covers was restored, it doesn't mean that their punishment is over.