Complex sentence: Balthasar Paul Ommeganck (sometimes also: Paul Balthasar Ommeganck; 1755--1826) was a Flemish painter of landscapes and animals who through his work and his role as a teacher was able to revitalize landscape painting in the Low Countries.
Split into simpler sentences: Balthasar Paul Ommeganck (sometimes also: Paul Balthasar Ommeganck) (1755--1826) was a Flemish painter of landscapes and animals. Through his work and his role as a teacher he gave an important impetus to the revitalization of landscape painting in the Low Countries.