Thanks for all the help. I really appreciate it. I believe in closing threads (for future searchers) so here's the outcome.
Never did find a cheap source for a Zener Diode. Individual diodes were dirt cheap, but most places had minimum charges, minimum quantities, etc. I would have liked to try that configuration as it seems the most elegant solution.
Instead, I put a second relay in the circuit so now there are two relays which trigger simultaneously from the ring detection circuit. One does the work I need. The second momentarily shorts across tip/ring with a 1200 ohm resistor, 5 watts, thereby causing the answer/hang up condition I was looking for.
Thanks again for the advice on the 1.2K ohm resistor. Not sure whether the 5 watts was overkill or underkill, but it was what I was able to get through serendipity.
