Q:

What to do with late answers which retread the same ground as previous answers (but not as thoroughly)? 

What is the correct course of action when reviewing late answers that, while technically correct, retread the same ground as previous (much more thorough) answers? 
A new answer to an old question popped up in the "low quality" review queue: Convert int to string? 
The question itself is nearly 4 years old and the existing answers thoroughly address the question.  At this point, it'd be an unusual answer that provided new, useful information not already covered by previous answers. 
There have been two new answers recently (one from today and one from April - since deleted).  The answers are simple one-liners covered by multiple previous answers.  But they fully and correctly answer the (really simple) question, so I'm not sure they're "low quality" in the context of the question.  
I'm not sure what the correct course of action(s) is/are, or if no action is necessary. 

Should they be downvoted?  Four years ago, they would've been useful and probably upvoted.  But not anymore, given the existing higher-quality answers. 
Should they be deleted?  These new answers don't need to exist.  But none of the reasons for deleting that show up in the review queue seem appropriate. 
Looking for an answer, I came across the guidelines for protecting questions, but that seems inappropriate since the question is not attracting spam or non-answer answers ("thank you", etc). 
Should  I just leave a comment asking them to elaborate, as their answers were already previously covered?  Really not much to elaborate on! 
Should they just be left as-is?  In which case, a year from now there could be a dozen more one-line answers covering the same ground.  Granted, they'll drop to the bottom of the post with 0 votes, but it seems silly to leave them there. 

In the end, I voted to delete them both. 
Checking back in the review queue, I see some reviewers going one way, some the other.  Generally weighted towards deleting, but again, I'm not positive that's the appropriate action. 

A:

Answers that merely parrot information that someone has already provided earlier (for some significant amount of time earlier) in lesser detail don't add any value. 
Cast a custom moderator flag, explaining the problem ("This answer is a duplicate of an answer already posted two years ago"). 

A:

From what I gather moderators are far from up-to-date with the housekeeping that only they or SE staff are authorised for.  Faster action from them (right or wrong!)  would be of general benefit.  So it is not desirable to rely on mods for what can be achieved without their involvement.  
And there is no need for their involvement in a situation such as described.  The key downvoting guidance is very simple This answer is not useful.  There is no way a duplicate answer (whether one second or one year later than what it duplicates) is other than  … not useful.   If you want to add ‘weight’ to one approach rather than another where more than one solution has been offered, upvote the better solution, don’t repeat it, nor condone others doing so. 
Downvote duplicates if they are just that – though bear in mind many answers may cover the same ground but add a fresh slant or cover a corner case, which is useful.  Where you have the privilege of downvoting duplicates do not flag. 
If two answers are the same and there is a time interval between them, downvote the redundant (ie later) one regardless of the duration between the answers.