First of all: sorry for the language, English is not my primary language.

I have star-like DNS structure with many filials (more that 2):

                                   ^
                                   |
                                   v

filialNS_1.filial_1.city.local <----> ns.main.city.local <----> filialNS_2.filial_2.city.local

                                   ^
                                   |
                                   v

• ns.mail.city.local is slave of all filials zones
• filialNS_1 is master of filial_1.city.local
• filialNS_2 is master of filial_2.city.local
• filialNS_N is master of filial_N.city.local

I want to:

1. serve DNS queries for xxx.filial_N.city.local with filialNS_N.filial_N.city.local
2. forward all queries for xxx.xxx.xxx.local from filialNS_N to ns.main.city.local
3. forward other queries to our provider's DNS on filial (or google-public-dns or anything else)

FILIAL CONFIG named.conf

zone "filial_1.city.local" {
        type master;
        file "/etc/namedb/dynamic/filial_1.city.local";
        allow-update {
                key DHCP_UPDATER;
        };
        allow-transfer {
                <ns.main.city.local IP address>
        };
};

zone "2.76.10.in-addr.arpa" {
        type master;
        file "/etc/namedb/dynamic/2.76.10.in-addr.arpa";
        allow-update {
                key DHCP_UPDATER;
        };
        allow-transfer {
                <ns.main.city.local IP address>
        };
};

zone "local." {
      type forward;
      forward only;
      forwarders {
                <ns.main.city.local IP address>
      };
};

nslookup server.filial_1.city.local - works fine

nslookup server.main.city.local

Server:         127.0.0.1
Address:        127.0.0.1#53

** server can't find server.main.city.local: NXDOMAIN

Where am I going wrong?