Those hack attempts are very specific hacks with intricate web of technologies to support it. The organization behind it spent a lot of effort and money in producing something that they could profit from it (i.e. getting accounts they can spam from). What this means for zenphoto users are that unless someone decides to target zenphoto galleries (which I could imagine very low btw.) the capthcha we have now is probably more than adequate for most users.
@williamz absolutely true, as I said I'd like to option of using both.
@acrylian if I had more than a passing knowledge of PHP I'd give it go but I don't hence my request.
FWIW I'm very happy with Zenphoto, I've tried pretty much every photo gallery script out there and Zenphoto is by far the easiest to work with.