Find login and password combo of our router


Job Description

Hi, we have a Zyxel 650H/hw-33 router.
When it was installed by the company installing everything on the network they have not given us login credentials.

I can reset the whol device so, everything is blank. and then I know the login password combo. But maybe someone knows a way to gain access to it somehow. As it is already an old model maybe there is a security leak inside to gain access to it? or other way you know of.

Else we need to install all settings again. Which might be some work.
So anyone who can help with this one?

or will it be impossible?