if TinyMCE (the note software) supports MahtJax it may be possible to do that in the future - Zotero is not currently using the most recent version. If TinyMCE doesn't have support then almost certainly no.
MathJax is simply a javascript lib that can be loaded via cdn or local install. Most webpages that use TinyMCE and Mathjax only show the MathJax renderings on the view version of the text (i.e. doesn't render dynamically in TinyMCE).
Some things like this seem to exist: https://github.com/efloti/plugin-mathjax-pour-tinymce (allows rendering the math in tinymce).
That's pretty cool. The main issue with integrating it is that the shortcut key to toggle the render mode wouldn't be discoverable, and I don't love the idea of adding another palette icon that only a very small fraction of people will use.
There's not too much of a downside to integrating with the shortcut key, of course — it just would likely get very little use.
Why do you think it will get little use? In all of the sciences there is math in the papers that are stored in Zotero. Math is crucial for good communicatiion about scientific literature. MathJax is now the defacto implementation of communicating with mathematical notation in HTML and is supported by the American Mathematical Society (among others). The notes in Zotero are the only way to communicate to yourself or others about the items in the database, that stays with the database (as opposed to writing on paper, scanning it, and attaching it). I don't have any data to prove it, but my guess would be that it would be used a lot.
It seems like If I copy a mathjax equation from web and paste it in a blank note,can't see anything,but on the middle panel The equation can display in the title of the note correctly! that means the mathjax rendering engine is already have in zotero,correct?but only not available in note?
Some things like this seem to exist: https://github.com/efloti/plugin-mathjax-pour-tinymce (allows rendering the math in tinymce).
There's not too much of a downside to integrating with the shortcut key, of course — it just would likely get very little use.
+1
Report customizer adds MathJax support for reports.