fix zipfile.py 'UserWarning: Duplicate name: docProps/core.xml'

src/docx/opc/constants.py

@@ -313,6 +313,10 @@ class RELATIONSHIP_TYPE:
         "http://schemas.openxmlformats.org/package/2006/relationships/metada"
         "ta/core-properties"
     )
+    CORE_PROPERTIES_OFFICEDOCUMENT = (
+        "http://schemas.openxmlformats.org/officedocument/2006/relationships"
+        "/metadata/core-properties"
+    )
     CUSTOM_PROPERTIES = (
         "http://schemas.openxmlformats.org/officeDocument/2006/relationships"
         "/custom-properties"

src/docx/opc/package.py

@@ -175,9 +175,15 @@ def _core_properties_part(self) -> CorePropertiesPart:
         try:
             return cast(CorePropertiesPart, self.part_related_by(RT.CORE_PROPERTIES))
         except KeyError:
-            core_properties_part = CorePropertiesPart.default(self)
-            self.relate_to(core_properties_part, RT.CORE_PROPERTIES)
-            return core_properties_part
+            try:
+                office_document_part = self.part_related_by(RT.CORE_PROPERTIES_OFFICEDOCUMENT)
+                rel = self.relate_to(office_document_part, RT.CORE_PROPERTIES_OFFICEDOCUMENT)
+                self.rels[rel].reltype = RT.CORE_PROPERTIES
+                return cast(CorePropertiesPart, office_document_part)
+            except KeyError:
+                core_properties_part = CorePropertiesPart.default(self)
+                self.relate_to(core_properties_part, RT.CORE_PROPERTIES)
+                return core_properties_part
 
 
 class Unmarshaller:

src/docx/opc/rel.py

@@ -134,6 +134,10 @@ def is_external(self) -> bool:
     def reltype(self) -> str:
         return self._reltype
 
+    @reltype.setter
+    def reltype(self, value: str):
+        self._reltype = value
+
     @property
     def rId(self) -> str:
         return self._rId