Hello,
You might be able to follow this PowerShell Script written by ChristianGarcia, which can be found here. Another option to burn ISOs is to use third-party software. Although you don't want to use third-party tools, ImgBurn, which is a very reputable application that allows you to read a DVD and make it an ISO file, but when you download ImgBurn, make sure that you choose Mirror 7, which is from ImgBurn's servers.
Hope to hear back from you.