This distinguished name still feels a bit ancient, but with the rise of such former graybeards as Jeremiah and Elijah, it also sounds child-friendly again, as does the Latin-Greek form Zacharias.
Zachariah is a name that was in fairly regular use by the Puritans of the sixteenth century, then was eventually and completely overtaken by the more modern sounding Zachary. But strange as it may seem, Zachariah and Zacharias now seem more au courant than Zachary (even though that name remains in the Top 100).
In the Bible, spelled Zechariah, it is the name of about 30 different personages, one of whom gave his name to the book of Zechariah.
Zarachiah Hobson is a character in the Thackeray novel, The Newcomes.
Zakkai, a Hebrew abbreviation of Zachariah, is another interesting option.