This zip file contains two files..
1- sitemap file called yourdomain.xml
2- css file called sitemap.xsl
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All you need to do is, extract the zip file and upload to your root domain.
You may change (yourdomain.xml) to (sitemap.xml)

This is a XML Sitemap which is supposed to be processed by Search Engines such as Google - Yahoo - Bing

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https://websiteseochecker.com/html-sitemap-generator/