If you are getting error for all zone files while restarting named service in DirectAdmin. The error seems your named script is corrupted.To resolve this error, you can follow the steps below which explains how to get new named script.
First Backup the named script that is already on the server.
mv named named_bak
wget -O named http://www.directadmin.com/named chmod 755 named /sbin/chkconfig named reset
Now, try to start named service