Although @admitrov gave you a nice, long answer that may be correct (I'm no linguist), as a native Pole never in my life have I heard a difference between rz an

Although @admitrov gave you a nice, long answer that may be correct (I'm no linguist), as a native Pole never in my life have I heard a difference between rz and ż. Same with ó and u, as well as ch and h. If there really* was a difference, native speakers wouldn't have so much trouble with ortography. *ch and h have historically been two different consonants but have gotten washed down into one.