Would "Niemożliwe to możliwe" be idiomatic?
No, I don't think that it works.
RU: Niewozmożnoje jest' wozmożno.
What's the significance of the "noje" part?
-ое (-oje) is the gender-neuter ending, such as "какое" = "which,"
Masculine would be "какой" (kakoj),
Feminine would be "какая" (kakaja).
OK! I get it now. The italic font which I see made "noje" look like a separate word from "Niewozmoż".
are these adverbs?
Not according to https://en.wiktionary.org/wiki/mo%C5%BCliwy . They appear to be neuter adjectives (just as in the Russian which va-diim explains above.
thanks, Jerry. But an adjective defines either a noun or a pronoun, which isn't the case here, I guess. So shouldn't it rather be an adverb?
Well, perhaps you can think of these adjectives as actually describing an abstract noun which isn't explicitly stated.
I can imagine an enthusiastic boss telling me that "the impossible is always possible, so get on with it!!" :-)
Should be the solution, you are right.
Besides: I now found the corresponding adverb, which is możliwie
zrób to możliwie szybko
(do it as fast as possible)