Look at how White’s pieces relate to Black’s king; see that he has two pieces trained on g7, a square adjacent to the king. White’s queen is about ready to mate there with support from his dark-squared bishop. All that prevents this is the protection g7 takes from Black’s queen on e7. This means the Black queen is inflexible, and the protection it appears to provide to any other pieces may be illusory. Look for something else it seems to protect and find the bishop on d6. White can play RxB for free.