If you have files with suffix .IDX in a directory /home/zaurus/Applications/dtm, you are doing DTM. For XML, I don't know where are the files and their names.
If you want to program, it would be feasible to write an application to migrate DTM <-> .pdb, but I don't know any application existing today and doing that. And given the fact that in a near future most people will probably migrate to OZ or some not Sharp ROM with different PIM applications, this may not worth the effort for someone to write such an application. And, of course, it's not in the genes of Z afficionados to ease the migration to Palm devices... Seriously, it requires some knowledge of .pdb which Z afficionados may not find very useful to acquire.