I posted the schematic in two parts at these URLs:
http://antiqueradio.org/art/temp/Zen...Schematic1.jpg
http://antiqueradio.org/art/temp/Zen...Schematic2.jpg
Big files, so I would right-click on the URL and save to your computer for easier viewing.
Looks like the chroma reference oscillator is a 6GH8.
I'm not going to keep those files up there forever, so get 'em now if you're curious.
Regards,
Phil Nelson