I'm not sure if the artist is Greg or not... I think he generally signs his work. I know the designs are from Pretzel-aki's koyukkuri, but the line style is completely different (plus as far as I know, all of Pretzel's work is in color)...
I think even the people at the yukkuri tracker get it wrong at times. Like with post #15226, that really doesn't match with z-aki's style (he has a completely different way of drawing gutter trash and eyes), but it's in the thread.
That said, this is one is probably still Pretzel-aki.
Hmm... maybe it'd be good to do a translation of the front page of the yukkuri futaba, that can be edited into a picture to show what section's for what. There's all these published, published_etc sections, but no idea what the difference is between them generally.