if you really have no idea what the user name and password are, then you probably will not get around a factory setting. you may be able to revive the wlan but you can change settings without access data never again.
I would not even try to revive it.
maybe you can still try to get the access data, but otherwise simply factory setting.
I think that the AP's connect themselves with the ZD, but I am not sure, but I can check that if nobody else knows this.
I wish you success