Stumped!
It certainly looks like Trewan. (I cannot, no matter what mental gymnastics I try to perform, imagine that it looks anything even remotely like either Greenock or Greenwell.)
The only Trewan I can think of in Scotland is in Dumfries-shire, near Dalbeattie, which is right down south near the Solway, and quite a long way away from any part of the boundary with Lanarkshire, so if he was from Trewan he couldn't be from Lanarkshire, and if he was from Lanarkshire he couldn't be from (that) Trewan.
I see that there is a death of Charles Henry Moore, aged 82, in 1945. This gives a birth date of 1862/3. His age on Francis' birth certificate in 1893 is 31, which gives a birth year of 1861/2. This is after the start of civil registration in 1855, so unless Charles Henry was the best part of a decade older than he claims on Francis' birth certificate, there should be a birth certificate. But the IGI (which is pretty much complete from 1855 to 1874 for Scotland) doesn't list anyone even vaguely matching. So we could have a case of a change of name.
Does his death certificate (or burial record) say when he came to New Zealand? If it was after 1871, there is a chance that he might be in the 1871 and/or 1881 census.