subdomain DNS issue

[yiutin03]

I have a domain abc.com, inside the forward zone, there are other subdomain under it, abc.com\sub1 abc.com\sub2, they are update the DNS record (e.g. got all msdsc srv record in the folder).

While we create the sub3.abc.com, it became is separate forwrad zone as sub3.abc.com and no longer update to abc.com\sub3.

How can I put back the sub3.abc.com to abc.com\sub3?

Thanks!