So how does Hindi handle questions with negative questions?
• answer as if there were no negation (नहीं would mean "no, this question isn't difficult"),
•answer it with regards to the negative (नहीं here negates the sentence as asked and means it is difficult), or
•get hopelessly confused like we do in English? ("Did you not see it?" "No." "No you did, or no you didn't?" "Yes." "Yes, no or yes, yes?"...)
That sounds a little odd to me, like Shakespearean style or something. I think "Is this questions not difficult" is the right translation in modern English.
I agree that Ken384225's answer also sounds odd. I'd say though "Is this not a difficult question" as the sentence which sounds the least awkward.