PTR format question

[groups]

In the process of cleaning up a much neglected PTR file

Bind:   9.6.2.1
OS:      CentOS 5.4

Current PTR in this format:  (1 tab between entries)

$ORIGIN 58.172.in-addr.arpa.
$ORIGIN 0.58.172.in-addr.arpa.
11    PTR    nat-172-58-0-11.example.com.
12    PTR    nat-172-58-0-12.example.com.
...
$ORIGIN 58.172.in-addr.arpa.
$ORIGIN 1.58.172.in-addr.arpa.
21    PTR    nat-172-58-1-21.example.com.
22    PTR    nat-172-58-1-22.example.com.
...
$ORIGIN 58.172.in-addr.arpa.
$ORIGIN 2.58.172.in-addr.arpa.
31      PTR     nat-172-58-2-31.example.com.
32      PTR     nat-172-58-2-32.example.com.
...

I have to redo the entire subnets.. it will be a very large file..

My question is this the "most efficient" way to do this..?

Thx
Charles