Cache is not at posted coordinates. There is no need to go to posted coordinates because it is on the water, you do not need a boat to get to the final.
The Zoo area also has many areas not visible from the outside of the zoo. Such locations include, Simmons Aviary, Hubbard gorilla valley and orangutan forest, Grewcock butterfly and insect pavillion, expedition madagascar, and Scott aquarium.
The final location is at
N 41 AB.CDA
W 95 EE.DCD