You could install the Export Report addon from the marketplace and use it https://github.com/zaproxy/zap-extensions/wiki/HelpAddonsExportreportExportreport#command-line
You could try applying the XSLT file that ZAP uses to transform the XML results to HTML: https://github.com/zaproxy/zaproxy/blob/master/src/xml/report.html.xsl - this is included in the XML directory.