It ain't the least bit fitting for Mal to think of Zoe this way, 'specially when he's in his cabin, doing what men do when they've been alone too long.
Images haunt him of that time he'd seen her naked from the back while an Alliance attack turned the valley below into a bonfire.
He tries to picture Inara. That hurts differently, but at least it don't violate a code.
His mind slips back to the one that ain't his to want, as he finishes and tries to tell himself it never happened.
Least ways, no one will ever know.