Zaishen bounty question

My ranger/monk has completed 4 of the five The Last Hierophant phases. Todays Zaishen Bounty is to kill Justiciar Thommis, which I've already done. If I accept this mission, do I have to kill Thommis again, does it affect my Quest status for The Last Hierophant if I don't kill him again?

Maybe someday I'll finally kill Duncan the Black but would hate to lose the progress I've already made.

Yes you do
No it doesn't

Thanks for the info.