Phew - this was not an easy one. I expected the bike path much more nearby than it actually is - and tried out many variations to get to GZ yesterday. After an indepth study of the area using Google maps, I tried it it again today, reached GZ easily but then had to look around a long while until I found it by accident. Nice box!
TFTC to Tankengine & BBBumblebee - Fogg