1kell:
the only funny thing i see is there is a table prefix for the old shopping cart, but none for zencart. If that would affect things???
The location of osc to zen scripts only need to be on a url that can access both the original osc database and your new zen database.
Backup both your databases, OsCommerce and ZenCart.
Edit import_osc_configure.php with the correct mysql server, database name, user, password information, table prefix (if any) and MYSQL Character Set code if needed.
Note:
The variables are set in one section for osc database (source) and the second set of variables are set for the zen database (target).
If your osc uses a table prefix enter it in $source_db_table_prefix = ''; variable.