Here is how to transition from 1-13 Worgen to Kalimdor 11-20

[AcidRaZor]

(nb, I'm a druid, so not sure if this applies to everyone, I think it might)

Accept/Complete the quest "Rut'theran Village" right after "Endgame" has been completed.
Load up Kalimdor 11-20 (since the last step loads some fictitious guide and doesn't transition from Endgame to Kalimdor)
Once you're in Rut'theran Village, accept "The Howling Oak"
Run into Darnassus (use Blizzard's built in indicators using the "Map") and hand in the quest.
Accept the quest "Breaking the waves of change" (This is what you need to start your journey on 11-20)

Hopefully the ride up the levels with Zygor will be smoother now

[Cartman]

Thanks for posting this, hopefully the Zygor team will test and include this to answer the many questions.