Erik - sorry for the confusion with the directory name change. You can consider it the last real "beta" incompatibility.
I had the same problem with old URLs, and came up with a one-time fix to change them all. Run this SQL:
`UPDATE wp_posts SET post_content=replace(post_content,'/zen/i.php','/zp-core/i.php');`
Or if you prefer the rewrite URL route...
`RewriteRule ^zen/(.*)?$ zp-core/$1 [R,L]`
Note: the rewrite rule will not work with any strange filenames, nor with subalbums. Subalbums would require something recursive... I just did the SQL after I realized that.