Well, no worries, the ZK is now sold.
Just as I was getting ready to post another pic to demonstrate corner to corner sharpness! When I have a good image that I'm prepping for print, I always do very careful sharpening via an edge-mask. Long ago, I created a Photoshop Action to make the basic mask for me, and when the alpha channel pops up, it's a great way to see what parts of the image are sharp. Every time I do this to an image from this lens, I am newly impressed. For example, here's what the edge mask looks like for the 4th ZK image I posted above, taken at f/4: