Hi Nurhan
There is no standard way to map the attachments and merge them. You will need to use a custom Java mapping to do so. The attachments can be accessed via InputAttachments interface.
You can search in SCN for sample coding on how to access input attachments. Here are just a few of such blogs.
Coding Java Mapping !!!! – Points to ponder
Attachments zipping during Mapping
I noticed that your attachments are XML files. Note that you cannot just merge XML files as is because the merged file would no longer be a well-formed XML file. You will need to think through how to extract the content from the four XML files to create the target XML file.
Rgds
Eng Swee