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And the 29-year-old Sydney-born athlete says he is out not only to win, but to set a course record.
McCormack grew up in New Zealand and still has family here.
"New Zealand holds a special place in my heart as it is the home of my mother.
"I lost my mother [Theresa] to breast cancer in 1999, and Wanaka was where my mother and father had their honeymoon.
" It is a special part of the world for me. I would really like to do something special at this race for these very reasons."
Challenge race director Victoria Murray-Orr said McCormack was regarded as the most successful triathlete.
"McCormack has won over 200 international races since 1993 across a range of distances and is the only athlete to break the magic eight-hour iron distance barrier more than twice.
"He has broken it four times."
McCormack is the current International Triathlon Union long-distance world champion and has also claimed the ITU world series championship title over the Olympic distance.
Defending champion, and fellow Australian, Aaron Farlow is also returning for the Challenge, as is 2011 champion Jamie Whyte, of New Zealand.
The women's field is once again likely to be dominated by four-time winner and 10-time iron distance champion Gina Crawford, of Wanaka.
The Challenge event is part of New Zealand's largest triathlon festival, involving over 2000 participants.