Regardless *maybe spoilers*
(tagged this for oldboy spoilers)
alright, i haven't seen the movie, so i can't exactly judge whether or not this is a true "ripoff" of oldboy. so i'll try to be as unbiased as i can.
there are levels of "stealing". i'm not sure what the levels are and i haven't developed a system for it. however, there are many things to consider in zinda in relation to oldboy.
again, i haven't seen the movie, so i don't know if it has the same "incest" plot. but let's put all that aside. i've read some of the posts on zinda and it seems incest is not part of plot at all.
but based on the trailer only, it looks pretty much like oldboy. the characters resemble those of oldboy. the outfits and style are similar. even the character torturing the other with a power drill is similar to that of dae su's hammer.
so, regardless of the missing incest plot line, there are obvious points that are being copied. and these aren't "homages" .. they're blatant ripoffs.