Well, 1st of all, read the description, it will say what ninja it can be used on, Kakuzu or Kakuzu [Earth Grudge Fear]

2nd, check the color of the book, EGF's book of Final Shot is Blue, while normal Kakuzu's is Gold

3rd, if you know Chinese, you can go check Tsunade NPC in CN version, they don't sell any books of any ninjas using gold vials, and neither do we!

So i suggest you go farm vials and procs, or his frags.