When you use Amazon’s "Download & transfer via USB" on their website, you are sometimes given a choice. For older eBooks (published before 2021), the download is often still AZW3, which converts to EPUB with zero issues (just use Calibre + DeDRM without the KFX Input plugin).

The conversion process from KFX-ZIP to EPUB can vary depending on the tool used. Here is a general outline of the steps:

A community-maintained plugin to strip DRM. You must download the latest release (e.g., v10.0.9 or higher) from a reputable source like the noDRM GitHub repository Configure DeDRM: In Calibre, go to Preferences File type plugins Customize plugin If using a physical Kindle device, select Kindle eInk ebooks and enter your device's Serial Number (found in device settings). Import and Convert: Delete any existing files from your Calibre library first. Re-import the book from your Kindle device or the My Kindle Content