That's probably because it's an unused general? I'm fairly sure that means they never made a challenge mode for that one. You can't unlock content that doesn't exist.
When I tried to play this faction in the challenges mode it brought me back to the intro screen but none of the buttons appeared. But I guess you're right.
To allow leang to be played as someone to fight as in challenge mode:
You need: finalBIG or some other .big editor
a text editor
(the game ofc)
In your zero hour folder in origin games (or where your origin games library is stored), find INIZH.big file;
make a backup of this file somewheres else (maybe in the origingames folder?)
open the original up in finalbig (or your big editor)
Go to Data\INI\ChallengeMode.ini and scroll to the bottom where it has "GeneralPersona9"
now where it has "StartsEnabled = no" change that to "StartsEnabled = yes" (change the no to a yes), now if you were just wanting to play her in skirmish, here is where you would stop, but since we want to play as her in challenge mode, this is not;
Where it says "Campaign = unimplemented" change that to "Campaign = CHALLENGE_9" This is where it is getting slightly unofficial; the devs never set a official playorder for Leang's challengemode, as it was just a boss general for them.
Find Data\INI\Campaign.ini
open it.
Go down to where it has the "Campaign CHALLENGE_8" block as you notice, there is no CHALLENGE_9 (yet), as we have to put that one in place.
Copy that whole block
and paste it right below it
on this new, pasted challenge mission list, change the first two lines to have CHALLENGE_9 instead of 8
From this point on, you can technically play as her ingame as an option, but note that we literally just used the same missionorder as the demo general, and if you want to add a touch of flavor and mix it up (and remove the humor of having leang vs leang as the last mission) you can change them.
At this point its all done, but to note, there is no "icon" or such for leang, so you have to mouse search for her (she is slightly above tao though)
