I'm sorry to say I believe that the Balanced TRRS connector will not work on an i9(not confirmed, but I was planning to confirm it in a week, since I don't have the Zeros in my hand right now). I have been speculating why cowon supported the balanced plug even though nobody use it, and I think I have found a reason:
Korea has this thing called DMB(digital multimedia broadcasting), it's like TV on a portable device like the Cowon, iriver, Samsung players or many Samsung, LG phones. What I think what happened is that Cowon tried to figure out how to increase the sensitivity and make the design better, and found out using headphone cables as antenna is good for the design(as there is no antenna that sticks out of the player), and using TRRS connectors is good for better reception(I have no idea how a TRRS connector does that, but many posts in the Korean forums say that). Now Cowon is trying to add support for a TRRS plug, but they didn't need a remote or a microphone, so they just added support for the balanced TRRS plug.
Now there's an exception-Cowon J3, which has a DMB version but still does not support the balanced plug, and I believe that the development of better DMB chips has eliminated the need of the TRRS plug for better reception.
Now, back to the reason I don't believe the i9 doesn't support the plug: the i9 does not have a DMB enabled version in Korea, and Cowon had no reason whatsoever to include support for any kind of TRRS plug.
All this is just speculation, but I am pretty sure this is the reason. Any other ideas are welcome.