Yesterday's changelog for the Kindle for PC update mentioned that you could use the app to zoom in on math equations, and now we know why.
Amazon released a new version of the (technical) Kindle Publishing Guidelines last week, and buried in the long and detailed changelog was a one line mention of MathML. This is a markup language that is used to write math equations in much the same way that html is used to format ebooks.
Amazon's KFX ebook format now supports MathML - mostly. The guidelines name seven tags that are explicitly listed as not supported, and there could be more that aren't mentioned (I have not been able to find a list of all MathML tags).
Edit: Actually, it doesn't support MathML at all. Amazon was being misleading when they said it was supported; what Amazon actually does is convert the equation to an image and display that.
what a joke to call "we'll run MathJax in an unspecified configuration and the generate jpg out of it" anything like "support". Makes my point from Ebookcraft that you can simply do this yourself and retain better control.
— Peter Krautzberger (@pkrautz) April 20, 2018
While Amazon had announced last December that screen readers could read aloud math equations in Kindle ebooks, there was no information at that time on how one would go about inserting an equation into a Kindle ebook.
Today's news filled in that knowledge gap.