In other words, I'm bone-tired — my body and my mind are both just wrecked.
Literal
In-other-words utterly-exhausted, heart [also-も] body [also-も] dead-tired [copula-です].
疲労困憊 (ひろうこんぱい) is a 四字熟語 'utter exhaustion,' a more dramatic sinitic alternative to plain 疲れた. クタクタ is a state mimetic for 'limp with exhaustion / dead-tired / worn out,' often said of the body but here extended to 心 'heart / mind' in parallel. つまり 'in other words / that is to say' is the summarizing discourse marker.