。
The question is whether he can do it.
Literal
Problem [topic-は] him [to-に] it [subj-が] able-to-be-done [whether-かどうか] [copula-だ].
Interesting structure: 彼にそれができる ('he can do it,' lit. 'to him, it is possible'). The potential form with ~にできる puts the possibility-holder in dative case. An alternative to 彼がそれをできる (which is also grammatical).