I had bought Asus ZenBook UX305CA in 2016 and the keyboard stopped working suddenly in 2019. I went to the service center of Asus and they gave me a quotation of Rs. 8000 which was a way too costly.
So I tried to use an external keyboard but even while starting the laptop there were random key presses and I was not even able to login with my windows pin. So I tried to open up the laptop myself to see if anything can be done.
This is a video of me opening the laptop and checking out the insides of it.
It is difficult to take out the keyboard without proper instruments as the keyboard is soldered on the machine.
One big negative about this laptop is that as the power button is part of the keyboard there is no way to start the laptop if something wrong happens to the keyboard. Your only way out is to get the keyboard replaced by a new one.
Eventually, I had to go to a local shop on lamington road called Dynamic technologies and they got it done for Rs. 3800.