The cache is not at the above coordinates. Don't go there, it's someone's front yard!
To find the correct coordinates you'll need to come up with the following values
A=HD 139669
B=HD 27894
C=HD 172167
D=HD 131873
E=HD 124850
F=HD 33636
The final coords are N 47 44.ABC W 122 12.DEF
GPS reception at GZ is a bit iffy. I made 3 trips there to get the coords, and got coords that were 30' different every time. Use the hint! No need to wander more than 5' off the trail.
You will need the number ABCDEF to access the logbook in the cache. If you don't sign the logbook, you haven't found the cache!
Congratulations for DM&K Cachers for the FTF!