What's the difference between ないわけにはいかない and ずにすまない？?


I think they both mean that you have to do something because there is a social
pression like なければならい、but I'm not certain that I can use them interchangeably.
Could somebody confirm it?




Come one natives! My best guess (yes, please downvote, as this site is not for
guesses, but I hope @Alex16 and I at least get someone to answer ;-) )

ないわけにはいかない has more of of the social pressure aspect (you are supposed to do
X) while ずにすまない more likely means that there are some more "rational" (*)
reasons for why failing to do X would cause problems.

(*) While it is "rational" to consider the other people when adjusting your
message, here, by "rational", I meant simply a statement made without
considering the "public opinion"

