According to the revision history of Specy Spooktacular, you appear to be the original creator of the annual event. You don't mind if I list Specy Spooktacular III as an episode of The Happy Tree Friends Show this year, do you? I won't change it at all.
The only difference will simply be the fact it is listed as a HTF show episode. Also, concerning your departure: it's sad to see you go, but your reasoning is well. Besides, even if they do a new episode I bet the creators won't be working on that much more of the series before they completely stop working on HTF just for Zwak, and then the quality will probably decrease. I'm sorta just losing hope in the canon series.