Complex sentence: Most of his work was to extend and improve railway buildings, though elsewhere he built the Zetland Hotel at Saltburn (1861--3), and the Royal Station Hotel at York (1877--82).
Split into simpler sentences: Most of his work was to extend and improve railway buildings. Elsewhere he built the Zetland Hotel at Saltburn (1861--3), and the Royal Station Hotel at York (1877--82).