What is the relationship between Mary mother of Jesus and Elizabeth wife of Zechariah?

They were cousins. However the Greek Word used was 'syngenis' which literally translates to 'relative'. so they were of 'kin' but not necessarily first cousins. according to the Word used to relate them in the scriptures, they could have been first cousins or even fourth cousins, it wouldn't matter. The important thing was that they were related.