The company says the creation of The Hits, with the star breakfast duo, will also inject international entertainment star quality in a special feature named The Scoop involving Gillespie interviewing stars.
Gillespie will also regularly appear on a ZM afternoon spot and on Newstalk ZB on Saturday mornings with Jack Tame.
"This is a major day for radio," said Jane Hastings, chief executive of TRN.
The new ZM breakfast team "have an off-the-wall sense of humour which is irreverent, creative and highly relatable. It works seamlessly with social media channels and they love connecting with their fans this way," she said.
Meanwhile Mediaworks Radio says TRN's award-winning breakfast host in the Waikato, Mark Bunting, will transfer to its The Breeze station.
Polly Gillespie and Grant Kereama will host TRN's new station, The Hits.