Creating and configuring subdomains (subdomains) in Bind Centos 7?

Question

Domain Name System

Hi everybody.
Given:
There is a domain abc.ru, everything works (resolving, mail, etc.)
Task:
Create subdomains: re.abc.ru; ra.abc.ru
Each domain has its own mail server.
The question is how to arrange the Bind configs, so that everything is good.
I've done it differently and it doesn't work. There is a resolution, but the mail does not go, or there is no resolution and everything no longer works. In the current configuration, there is no resolving to subdomains.
How it is done (what is now):
/etc/named.conf zones are
registered
abc.ru.zone
re.abc.ru.zone
ra.abc.ru.zone
abc config (edited 100500 times and the brain explodes)
/var/named/
$ TTL 86400
@ IN SOA ns1.abc.ru. root.abc.ru. (
2017041801 ;Serial
3600 ;Refresh
1800 ;Retry
604800 ;Expire
86400 ;Minimum TTL
)
IN NS ns1.abc.ru.
ns1 IN A 1.1.1.1
abc.ru. IN A 1.1.1.1
;
@ MX 10 mail.abc.ru.
mail IN A 2.2.2.2
@ IN A 1.1.1.1
;
re.abc.ru. IN A 1.1.1.1
;
ra.abc.ru. IN A 1.1.1.1
;
abc.ru. IN TXT "v=spf1 +a +mx ?all"
and, accordingly, subdomain configs in
/var/named/
$TTL 86400
@ IN SOA ns1.re.abc.ru. root.re.abc.ru. (
2017041801 ;Serial
3600 ;Refresh
1800 ;Retry
604800 ;Expire
86400 ;Minimum TTL
)
IN NS ns1.re.abc.ru.
ns1 IN A 1.1.1.1
re.abc.ru. IN A 1.1.1.1
;
@ MX 10 mail.re.abc.ru.
mail IN A 2.2.2.2
;
re.abc.ru. IN TXT "v=spf1 +a +mx ?all"
Questions:
How would you do it?
What can be changed?
Where are the mistakes?

Answer 1

you created hosts, not subdomains. Delegate
re.abc.ru.
IN NS ns1.abc.ru.
IN NS ns2.abc.ru.
ra.abc.ru. IN NS ns1.abc.ru.
IN NS ns2.abc.ru.