I finally got things work fairly ok:

I edited Makefile.PL with:
   my %DEF_FLAGS = ('GL'        => 0, 
		    'SHAPE'     => 1,
		    'GL_DAMAGE' => 1,
		    'ATC'       => 1
		     );

  ie using GL_DAMAGE instead of GL

  Then:

  make clean
  perl Makefile.PL
  make
  make install

  rebaseall

  perl demos/zinc-demos

  I still get "Use of uninitialized value" errors
  but this seems to be a "common" Tk issue.

  Most of the remaining issues are X-Server related
  eg "GLX not available..." runtime warnings

  I still have 1 annoying issue:
  The following works:
    my $zinc = $mw->Zinc(-width => 500, 
                         -height => 500)->pack();

  The following doesn't work:
    my $zinc = $mw->Scrolled("Zinc",
                             -width => 500,
                             -height => 500,
                             -scrollbars => 'oe')->pack();

  I get:

GLX not available (need at least a 24 bits buffer with stencil)
Use of uninitialized value $id in delete at
        /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/After.pm line 87 (#1)
Tk::Error: Can't set -height to `undef' for Tk::Frame=HASH(0x1ed4da8): bad screen distance "" at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Configure.pm line 46.
 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 294
 Tk callback for .
 Tk callback for .frame
 Tk callback for .frame.ysbslice
 Tk callback for .frame.ysbslice.corner
 (processing "-height" option)
 Tk callback for .frame.ysbslice.corner
 Tk::Derived::configure at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 306
 Tk::Widget::new at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Widget.pm line 205
 Tk::Frame::AddScrollbars at blib/lib/Tk/Frame.pm (autosplit into blib/lib/auto/Tk/Frame/AddScrollbars.al) line 242
 Tk::Widget::Scrolled at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Widget.pm line 1280
Can't set -height to `undef' for Tk::Frame=HASH(0x1ed4da8): bad screen distance "" at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Configure.pm line 46.
 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 294

 at /usr/lib/perl5/vendor_perl/5.10/i686-cygwin/Tk/Derived.pm line 306

Seems to be a problem with Tk + Scrolled + Zinc
Other scrolled items (HList, Tree) work fine.

Greetings!