Complex sentence: He learned the trade or craft of woodblock engraving as an apprentice on John Fairfax's "Sydney Mail" from 1891, then as zinc replaced wood as the engraving medium became a staff artist, succeeding Norman Hardy as their principal artist in 1897.
Split into simpler sentences: He learned the trade or craft of woodblock engraving as an apprentice on John Fairfax's "Sydney Mail" from 1891. When zinc replaced wood as the engraving medium, he became a staff artist, succeeding Norman Hardy as their principal artist in 1897.