porting from Win32 (or WinCE)

Hi there;

We are looking at the feasibility of porting - in process
of a general migration of in-house apps from Windows
to Linux) a rather large, but very clean, C (not C++ !)
WindowsCE program to Zaurus. (There are actually both CE
and Win32 versions). The GUI functionality is quite modest
(point/line/area drawing surface, some dialogs etc.) and
quite well isolated from the rest of the application code.

Is there:

1) Any documentation addressing specifically
the porting of either Win32 or WinCE code to Zaurus?

2) Any way to program Zaurus GUI applications in C ?
(re-coding the whole lot in C++ or Java is
unfortunately not an option).

(looked for either, seems we're out of luck on
both counts, but before we give up on this...)

All comments, either to the list, or to the mail
are much appreciated.

TIA, R. Kelly