Courtesy of astrohiker - "Head up Greenmount Hill on Gt Eastern Hgy. Turn left into the first entrance into the John Forrest National Park rd. THE ROAD IS LOCKED DAILY AT BOTH ENDS AT 4PM, & they want you out by 3.45pm. If you go past the turnoff you can take the 2nd entrance & work your way back to get his cache and then the Perth City lookout.
Unusually there is a forked grass tree here. This is very close to GZ but the cache is not in the grass trees.
You can park alongside the cache, but be careful of traffic, otherwise there is a good spot to park 200m east.
Enjoy the views!