Complex sentence: Dom de Vic died in 1734, leaving Dom Vaissette in sole charge of the great work, which he executed with success and which was published in four more volumes, the fifth appearing in 1745.
Split into simpler sentences: Dom de Vic died in 1734, leaving Dom Vaissette in sole charge of the great work, which he successfully executed. The work was was published in four more volumes, the fifth appearing in 1745.