The references on the site I linked to earlier, and the entries for similar items on ebay, etc... all say "tsukuru", and I'm inclined to think tsukuru is right because its a maker's mark and not an adjective used to describe the porcelain. Actually my guess would be either "zou" or "tsukuru", but the consensus seems to be tsukuru.
The consensus might very well be wrong. Toritoribe-san probably knows...