Well I think they could do "Zora" as this punky, slightly psycho girl. Like Sawyer from Black Lagoon but less emo-looking and with a maniacal grin rather than a blank, empty expression.
Zoro IS slightly pscycho when he's fighting. He loves fighting and gets a crazy grin as he does so, even if he's about to die. This Zoro genderswap has him with some dopey, slightly clueless look. Female Zoro looks like some over-the-hill big sister, doting on her younger sisters. When a fight starts, female Zoro looks like she'd say "No Luffy and Sanji! I don't want you to tear those clothes! I've already repaired them once today, you silly girls!"
And I say "punky" because it'd be a girl with incredibly short, green hair, who wears black trousers tucked into a big pair of black boots.
Zoro is as "extreme" as Luffy when they're both in a heated battle. So no real point in portraying that situation in their "regular state" female forms.
Zoro's "regular state" is that of the slightly dodgy-looking, big-brother style, as most of his "speeches" and advice to the younger members of the crew, often prove. The "big sister" role, fits ZoroKO (or Zora) very well.
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