The only explanation I can come up with for the tight gearing on the EEZZ D3 is that Dahon, after going to the trouble to engineer a pretty fly hydroformed aluminum frame for this bike, expediently used off the shelf Shimano Capreo cogs. To match the range of a common 3-speed IGH (a compromise that's worked well for 100+ years), the cassette would need to be a custom 9-12-16T.

With a rear OLD of 76mm, it's not like any other hub will fit. About the only gearing mod would be a $chlumpf geared crank.

Dahon seems to envision the EEZZ as a 'last kilometer' bike, and they've taken pains to make this intriguing platform sub-optimum to use in any expanded application.