Ok, I know there are a couple of old posts on this topic. I only saw two with the search function, sorry if there are others I missed, but those were slightly different, pointing out that if you hearth from Peak of Serenity, you retain the ability to use Zen Pilgrimage: Return.
(OLD POSTS ON THE TOPIC CREDIT:
http://www.ownedcore.com/forums/worl...ne-kindof.html
http://www.ownedcore.com/forums/worl...use-later.html)
If you use Zen Pilgrimage to teleport to Peak of Serenity from Stormwind and use the Stormwind portal (near Peak of Serenity daily questgiver) to return instead of Zen Pilgrimage: Return, you still have your hearthstone AND Zen Pilgrimage: Return available, both of which can port you back to Stormwind (or wherever you hearth to) at any time.
Or, if you use Zen Pilgrimage from any other location (as pointed out by old posts)(i.e. while questing and you want to buy something from AH, learn next level of a profession, etc.), and use the Stormwind port from Peak of Serenity instead of hearthing or Zen Pilgrimage, you get a free trip to Stormwind, a free port back (Zen Pilgrimage: Return) and still have your hearthstone.
The same applies for the Orgrimmar portal/Horde.
The difference between my post and the quoted posts is that theirs' involved being summoned or using your hearthstone to leave, and this method doesn't use any CD's.
Feel free to move this to General if it should be moved - I wasn't sure if this was intended, as it would seem to me like the devs would mean for the ability to use Zen Pilgrimage: Return to be removed upon use of the capitol city portals. Just trying to contribute a little and point out some useful uses of game mechanics, whether they're intended or not.