Meaning: will definitely/certainly do something; cannot not ~

JLPT N1 Grammar: ずにはおかない / ないではおかない (zu niwa okanai / nai dewa okanai) Meaning
Meaning: will definitely/certainly do something; cannot not ~
Meaning: one can even say that; it can also be said that ~
JLPT N2 Grammar: なくはない / なくもない (naku wa nai / naku mo nai) Meaning
Meaning: it’s not that; I may (double negative)