Mosfet Gate Resistor
(96V - 12V) across 470 ohms is 180mA through your zeners. That is 12V * 180mA = 2.16W dissipated in the zeners. I don't know what zeners you have but that's probably near the zener's limit so you probably do want to increase the resistors.

Your resistors are also dissipating power so they also will heat up more unless you increase resistance. About Four times more due to the voltage doubling if you leave the resistance unchanged.