When in the heart cycle is the shock delivered during cardioversion?

Sync or non-sync: It depends whether it is synchronous or asynchronos. Synchronous is when the shock is delivered on the qrs portion of the heart cycle - it is when the heart depolarises. Asynchronous cardioversion can occur anywhere on the heart cycle.

Into the QRS: The shock is synchronized to the exact moment that the cardiac muscle is depolarized which corresponds to the qrs complex on the ekg.