What was Abel Tasman's greatest achievement in exploration?

In August 1642, the Council of the Indies, consisting of Antonie van Diemen, Cornelis van der Lijn, Joan Maetsuycker, Justus Schouten, Salomon Sweers, Cornelis Witsen, and Pieter Boreel in Batavia dispatched Tasman and Franchoijs Jacobszoon Visscher on a voyage of exploration to little-charted areas east of the Cape of Good Hope, west of Staten Land (near the Cape Horn of South America) and south of the Solomon Islands. One of the objectives was to obtain knowledge of "all the totally unknown" Provinces of Beach. This was a purported yet non-existent landmass said to have plentiful gold, which had appeared on European maps since the 15th century, as a result of an error in some editions of Marco Polo's works.

The expedition was to use two small ships, Heemskerck and Zeehaen. Tasman proved that the small fifth continent was not joined to any larger sixth continent, such as the long-imagined Southern Continent. He actually thought he had found the western side of the long-imagined Terra Australis that stretched across the Pacific to near the southern tip of South America. He was the first known European explorer to reach New Zealand and the islands of Fiji and Van Diemen's Land (now Tasmania).