[morzh]

If using zeners I would use zeners with a wide range Iz. They should withstand the power equal Iz-max times Uz at about 14-15mA.

Then I would put two in them that are 68V in series, and in addition serialize a 3V and 7V zeners. Reference the point where the two connect to the lower 68V zener as a GND.

You will need a separate power source for 2V filaments. Could try AC, but filtered DC is cleaner.

Why 15mA?

Your B+ battery drain is 8-12mA and you need the zeners to withstand this current without load. The zeners should preferably still stabilize at about 2-3mA of current, which will be the case when the load is connected.

However Zeners are bad regulators to power up things - they are mostly used as references, so if you could make a clean DC power source, that would be better.

Again you need all voltages at low current except 2V (700mA).