While I can't claim personal experience with either of these two ladies BCD's, (where they are curved, I'm warped) I can tell you the feedback I've gotten from customers who have tried both. While both are excellent BCDs, after actually trying both, many choose the Zena. The reasons given are 1) The Zena's rip cord system is easier to use than the Hera's buckle system, especially in cold water while wearing thick gloves. 2) The Zena is more comfortable all round, but especially when inflated. The Hera has the "squeeze effect" associated with all jacket BCDs when it's fully inflated.. 3) The Zena has more weight capacity - 34lbs total vs 30 lbs for the Hera. 4) The Zena's contoured fit is more streamlined than the Hera. The split is around 80% for the Zena and 20% for the Hera.
Your best bet is to "try before you buy" if at all possible.
Let me know how you make out!
Safe Diving,
George
PADI MSDT