Compressing images in an Excel workbook is very similar to in PowerPoint

Quite a while back, I devised a PowerShell script to convert all images in a PowerPoint presentation to JPG and compress them. More recently, someone needed to do the same thing, but for an Excel workbook. It turns out that XLSX archives have essentially the same structure as PPTX archives except that Excel-specific data is under the xl folder instead of the ppt folder for PowerPoint. Word DOCX archives use word, so the script should also work for them after tweaking the path.