Python: Unzip the file, apply modifications on the containing files and zip the file again

I have to write a filter for files in a zipped file. So I have the zip file as an input, it contains some xml kind of files. I filter the xml with xslt. So the files will be overwritten and finally zip the file again. My code looks like the following:

Problem: Terminates without exceptions but It does not work.

from lxml import etree
from io import StringIO
import zipfile

def axlFilter(inputfile):

    with zipfile.ZipFile(inputfile) as zip_file:
      for file in zip_file.namelist():
          try:

              xslt_root = etree.XML('''\
                <xsl:stylesheet version="1.0"
                xmlns:xsl="http://ift.tt/tCZ8VR"> 

                <xsl:template match="node() | @*">
                  <xsl:copy>
                      <xsl:apply-templates select="node() | @*"/>
                  </xsl:copy>
                </xsl:template>


                <xsl:template match="TimeStamp"/>
                <xsl:template match="@timeStamp"/>
                <xsl:template match="TimeStamps"/>
                <xsl:template match="Signature"/>

                </xsl:stylesheet>
                ''')

              transform = etree.XSLT(xslt_root)

              doc = etree.parse(file)
              result_tree = transform(doc)

              resultfile = StringIO(unicode(str(result_tree)))
              zipwrite.write_file(file, resultfile)


          finally:
              zip_file.close()