Families of Early Milford, Connecticut (my go-to source for Milford families) is clear that Mary Burwell is the daughter of the first wife of John Burwell. And John Burwell, son of John Burwell, might be also the son of the first wife.
Zachariah is named as a son of Alice Heath on John Burwell, the father's profile, but several people have recently asserted that he was also the son of the first wife, Esther Winchester.
Does anyone have a reliable source for his mother?