The arrows showing the direction of current flow through the zener diode circuit exampes should be going the opposite direction. The zener diode operates in reverse bias, so the direction of the arrow of the zener itself is correct, but the current directions should never go into the + terminal of the DC power supply. Since the zener operates in reverse bias, the direction of the current will flow in the opposite direction of the arrow in the zener symbol.

 

Observe the applied voltage and it seems as if the zener is operating in reverse bias, as it should.