I did exactly same as you have explained in example but i am getting same error every time.
Directory.
DocxMerge\libraries\TbsZip ERROR with the zip archive: File "word/document.xml" is not found in the Central Directory.
DocxMerge\libraries\TbsZip ERROR with the zip archive: File "[Content_Types].xml" is not found in the Central Directory.
DocxMerge\libraries\TbsZip ERROR with the zip archive: File "word/_rels/document.xml.rels" is not found in the Central
I did exactly same as you have explained in example but i am getting same error every time.
Directory.