Zachariah was already married by the 1850 census, but he was living next door to his parents, and the names are so similar that I thought it was worthwhile making a note of them:

1850 census of Fleming Co., Ky, division 2, enumerated 15 Aug, lists as family #68:
Zachariah Phelps, 71, farmer, b. Va; Martha, 61; Druzilla, 29; David L., 26; Minerva, 20; Mahaley, 17. All except Zachariah born in Kentucky.

Rowan Co., Ky birth records list Elizabeth Colwell, born 27 Aug 1857, father Jackson Colwell, mother’s maiden name Mary Adams.

Her maiden name is also spelled as Calwell and Caldwell.

Rowan Co., Ky marriage license book 1, p.103, and register book A, p. 6, record the marriage on 30 Nov 1886 of Z. R. Phelps and Elizabeth Purvis, at Elizabeth Purvis’s by H. G. Alderson, witnesses Harrison Padgett (also bond surety) and Jackson Cawell (probably intended Colwell or Caldwell.)

Strangely, there is a consent note attached signed by Elizsiebeth Purvis, presumably giving her consent to her own marriage.

1900 census of Rowan Co., Ky, Farmers precinct, enumerated 26 June, lists on pp. 22A-22B as family #388/393:
Phelps, Zachrire, 74, b. Oct 1825, Ky Va Ky, married 52 years, farmer; Elizabeth, wife, 42, b. June 1887, married 13 years; Geo R., son, 13, b. June 1887; Isaac T., son, 10, b. May 1890; Purvis, Joseph W., stepson, 19, b. May 1881, farm laborer; Leolie, dau, 15, b. Nov 1884. All except Zachariah born Ky Ky Ky.

Leolie should be recorded as a stepdaughter.