Moral of the story is that some things are too cheap... Buy something better for a bit more.
I've a older spec smaller Zen V Plus (4 Gb, Black with Blue trim). This charges perfectly fine from a USB to PC cable.
This plug does not charge the Zen V Plus. It turns Zen on when plugged in, but the player does not charge (left for one hour, and then overnight with no effect).
I've also got a newer type large Zen V Plus with the bigger screen (4 Gb with Micro SD Card slot). This does charge, but it takes 24 hours to fill to full power, when it only takes 4 hours empty to full on a USB PC Cable.
This charger just seems to be underpowered and insufficient for charging.