For the time being you probably have to use FBX as an intermediate format to bridge blender versions, as a backport of cobra tools is impossible and a rewrite of the ZT1 sprite tools is not planned.
Thank you for your quick answer. Yesterday I merged some ztd files and deleted some more, now I have a burger stand and drink stand. Maybe I had too much ztd files? (I had 348, now I have 30)