What is the rating current of zener 1N702
The 1N702 was a 400mW zener diode. Izt is 5mA for 1N702~1N707.

This is a particularly horrible example, by the way. A 2.6V zener operated at 5mA will make a really lousy regulator.
Distinguish between Izt (the current at which the zener voltage is guaranteed) and the maximum zener current, which will be limited by power dissipation. It will be a bit hard to estimate for the 1N702 because the voltage will be much higher than 2.6V at the maximum current, so the latter will be well under the 80mA you might expect were the voltage to be constant with changing current.

P.S. I really have to wonder whether the part number is a typo and they really intended to specify a 1N711 7.5V zener, which would make a lot more sense.