Chinese maps could re-write history

This article about the rise of Chinese map collectors sparked my interest when it appeared a few weeks back. Now one of these collectors has unearthed a 1763 reproduction of a 1418 map, which suggests the Chinese mariner Zheng He reached the Americas before Columbus, and charted parts of Antarctica and northern Canada. The collector, Liu Gang, says he'd been in possession of the map for 4 years, but only deciphered its importance when he read Gavin Menzies' 1421: The Year China Discovered The World. Menzies' book proposes that European map-makers copied ancient Chinese maps, which subsequently aided the great European explorers such as Columbus, Mahellan, Da Gama, and Cook. This thesis has been disputed by historians who criticise its lack of evidence. Could this be the evidence Menzies needs?