With this syntax, at first there doesn't seem to be an object though. But it could also be said, "it is difficult to answer the question." Then the question is clearly the object of "to answer." Anyway, I found this structure really difficult to understand; well, unusual at least.
The construction "is[/am/are] to be" is used not to describe but to stipulate something that has not yet come about, e.g. "The house is to be painted blue." It can also be used to give a suggestion, as a softer alternative to using the imperative mood, as in "This movie is not to be missed".
So, firstly this is not the meaning that we want for this translation, and furthermore, "The question is hard to be answered" is ungramatical. It is possible to say "The question is to be answered", and if we want to stipulate further details, we would need to use adverbs or adverbial phrases, such as "The question is to be answered truthfully". However, once you use an adjective in "The question is hard...", you are already in an entirely different construction that doesn't go along with "...to be answered".