Brick zyxel ex5601-t0 help

Hi, I updated the firmware via the web interface of my zyxel ex5601-t0 modem but unfortunately it is brick. I bought a usb ttl to connect it to the computer with the pins, I managed to connect but it asks me for the password to access, I tried many passwords such as root admin. Can you tell me which one it is? The modem doesn't work, I can't access or any other way, only via USB serial but I need the password. I attach a screenshot

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