Interesting responses so far.
But if Zero considers himself not to be possessed any more, who are we to say otherwise? Stranger things have happened - e.g. Dalamar setting up with a moose, small shrubs popping up all over the Rankings, etc. etc.
So my considered opinion is if Zero does not think he is possessed, and there is no obvious evidence to the contrary (like there isn;t now), let's take him at his word.
Thus, Zero, you are no longer possessed.

Guiliayme

Penned by my hand on the 4th of Mayan, in the year 261 AF.