Muhammad pbuh IS the last law bearing prophet..but Rasululah saw also prophesised return of Isa. As first Isa has died a natural death, another person will come in his name.
This is not a new concept. When Jesus declared himself Messiah for Jews, Jews demanded to see Elijah (Hazrat Ilyas) who although having passed earlier was prophesised to return with Messiah. Jesus pointed at John (Hazrat Yahya) and said he is Elijah (ie John has come in the name of Elijah, as Elijah having passed already can not return according to Allah’s law that dead can not return). At this Jews rejected Jesus as they demanded to see the original Elijah and not another person in has name.
Jesus explained: