TLV1805-Q1: How the external protection parts work?

Part Number:TLV1805-Q1

Hello,

Would you please explain how the D4 Schottky between IN+ and IN- works? And in what situation? In the datasheet this is for an event like reverse supply, but I cannot understand what is the concern.

I would also like you to explain how the D6 Zener across the load works. I cannot understand how floating load can turn on the FET.

Thanks.

Oguri (TIJ automotive FAE)