。
Is it possible to change the return date?
Literal
Return-date [object-を] change do-[thing-こと] [subject-が] can [question-か]?
The longer potential construction ~することができる — nominalized with こと and marked with が as the subject of できる. Functionally similar to the contracted 変更できますか but slightly more formal and explicit. Official documents, business contracts, and written contexts tend to prefer this fuller form.