I think there is an air pressure sensor that gives altitude info but I haven't definitively found a source for that particular info. Micro fiche part breakdowns for the Zed show several unidentified sensors in the mix.
You certainly don't need an O2 sensor to adjust for altitude.
I believe the Vulcan line up uses just an air pressure sensor to get the job done here in the States.
From Motorcycling USA:
2009 Kawasaki Vulcan 1700 Nomad
The Nomad's fuel injection system, like those in use on Kawasaki's NinjaŽ 650R and Vulcan 900 motorcycles, utilizes one sensor in place of the usual three for less complexity and weight. Beside the obvious FI advantages like improved fuel economy and automatically adjusting for altitude changes, the system also permits easy hands-off warm-up and idle speed control.
This implies 3 sensors in old systems like the 3 shown in the microfiche for the zed simplified to one in the newest systems.
I'll try to find an answer,
rick