What does "as" mean in "than as that of"

"Fingal and Temora are better understood as the work of an eighteenth-century poet than as that of a third century one."

In this sentence, the word "that of" replaces the word "the work of" - which means the two clauses run parallel, as John pointed out. This choice is rather formal.

Informally speaking, the other clause can read "...than as a third century one's..."