Yes, I didn’t notice the lack of the resistor at the left. If the device input can tolerate the very large resistor shown after the diodes, then a similarly large resistor to the left can be used. A single Zener will conduct in both directions (negative to ground through the PN diode and positive to ground through the Zener). This is not used for fast or critical inputs, due to high capacitance and leakage current of the Zener.