added zyxel hard coded credentials (see https://www.zdnet.com/article/backdoor-account-discovered-in-more-than-100000-zyxel-firewalls-vpn-gateways/)
added zyxel hard coded credentials (see https://www.zdnet.com/article/backdoor-account-discovered-in-more-than-100000-zyxel-firewalls-vpn-gateways/)