Then you think about in wrong. Place the zener parallel to the cap but with the anode to the negative side of the cap. The zener will only START to conduct when the zener voltage is reached. Before that it's just high impedance and does nothing.
Then you think about in wrong. Place the zener parallel to the cap but with the anode to the negative side of the cap. The zener will only START to conduct when the zener voltage is reached. Before that it's just high impedance and does nothing.