@dultojorze and @guy038,
Shame on me! My intention was that my reply be completely embedded in a literal text box!
If you're confident every line starts with that exact 17 character sequence, we could start by matching that (for removal) with one of these:
^\Q0.0.0.0 0.0.0.0.\E
^.{17}
From there, we want to match the trailing "word1.word2" on the right (you're confident that in every case exactly that form is what needs to be preserved, right? so zero cases like "hello.world.com", right?), so we'd want to match (and capture) that after skipping everything to the left just before the second last word: .*\<(\w+\.\w+)
So altogether, and enforcing start & end of line boundaries, we can use this regex for Find
^.{17}.*\<(\w+\.\w+)$
and then we'll replace it either without the prefix
\1
or we'll replace it with the prefix
0.0.0.0 \1
After that, you can use Remove Duplicate Lines, a command in the Line Op group under the Edit menu. And you should be good.
Anyway, now there are two tested solutions.