I'm not sure this Zachariah of Orange County, NC is the father of the Thomas who married Margery Bryan nor of the Zachariah who lived in Davidson County, TN.
There's just not enough data yet found to prove anything other than two men were named Zachariah.
Likewise, we have a disconnect between Zachariah b. abt. 1706 and this one.We haven't proven they are related.
I, too, would like to see a photocopy of the will to check out the questionable areas in the transcription.
Several things seem apparent in this will.First, the separately listed children are certainly adults, except John who is still under 21.Three are given a shilling and the fourth gets parts of the estate.I'd guess the three had already received their inheritance or dowry.It's possible that Elizabeth is married to John Thomson, but I'd think the will would have noted that.
The other children may be minors, including Zachariah.The fact that all the girls appear unmarried lends credence to that assessment.This structure for a will was fairly common back then.I.e., To name the children by eldest first.