Hello! :)
I did this quest today (8/18/18) then the follow-up quest ("Best in Show") and I assumed for each the 3rd Zep was bugged. But then I read a suggestion to use a macro like "/target Paper". Things about these two quests I learned that may be helpful:
1. Use a macro, so basically when you hear that a Zeppelin is released, use it and then hit three for the bola. Don't have to stop jumping to search for or chase the stupid thing. Yes, you're riding a vehicle but if you have a keybind for a slot put the macro there and it will still work even though you can't see it. The third Zep appears something like one to two seconds before the timer expires so again practice the targeting macro + the 3 for bola for those points if you need it. For 150 though you don't need the third Zep even if it does bug out, the 50s from the other two and steady jumping for styles buffs to pop barrels will be enough.
2. Stay in the center of the ring and jump over the middle fences back and forth. Another poster suggested this for "Best in Show" and it helps a lot as you don't have to risk resetting the event by getting too close to the edge of show area. Just jump two middle fences over and over and pop the nearby barrels as they reset and macro + 3 key each announcement of a Zep. If the nearby barrels aren't up it's OK just stack more style buffs, one will be up soon.
3.No need to use charge. Just jump, jump jump, pop, jump, jump, pop, jump jump, jump, jump, pop... etc. and kill each Zep as soon as you hear it announced. Rushing too fast means missing jumps and missing targets when you strike at barrels, or even getting too close to the edge of the event and having the whole thing reset. A simple and steady back and forth in the middle will get the job done.
Good luck!