Conquest of the Horde

Greetings everyone, I'm working on a Troll character at the moment, and I'm missing an essential piece of data that I wasn't able to find while doing my research. So I will now ask you guys:

In what year did the witch doctor Zalazane betray the Trolls in the Echo Isles? How long did it take him to gain full control of the area?

Be a dear and help a fellow mon out.

I may be wrong, but I don't think there was an exact given year. It was shortly within the Horde founding Durotar, though.

Thanks

wiki.conquestofthehorde.com/timeline