This cache is a little different than most puzzle caches. The difficulty is often based on the difficulty of the puzzle. In this case, the hide is far more difficult than the puzzle, so the rating is mainly for the hide.
Now, a little about the puzzle. Everything you need to figure out the final coordinates is on this page. You do not have to leave the page for any information. It's not in the source code, so don't bother going there.
A little about the hide. The container is a bison tube that is not hidden in an ordinary fashion. The bison tube is inside something that inspired the name of the cache. Then that thing is hidden inside something else. Part of the difficulty is because of the number of places at GZ to hide a bison tube. Good luck.