Assumptions: Zanshin procs about the same rate as Double Attack (according to ffxicyclopedia) - 10% of the time. On missed hits, of course. Giving this strap the best case scenario (low acc = more Zanshin), acc is 80%. That means that 10% of 20% misses proc Zanshin, which equates to 2% extra swings.
Experiment: I will hypothetically give this item the astronomical boost of Zanshin + 10% proc rate (aka doubling its non-enhanced power). Doubling the previous Zanshin rate, that gives us a 4% extra swing count. This 2% boost in swings would be equal to the 2% Double Attack boost from a Pole Strap. Problem is, the assumption of 80% acc and the astronomical boost I gave it.
Conclusion:
Summary: Unless SE just released an amazingly potent Zanshin enhancer into the game, this is worse than Pole Strap.
*Van Halen's 'Girls, girls, girls' plays in the background*
To say nothing of what missing so much that you need an enhanced Zanshin would do you your epeen.