Accessible hotkeys for superscript and subscript

I want to add a feature of making text super- or subscript to a WYSIWYG text editor in my web application and I need to set up hotkeys for it. Popular editors like Microsoft Word use <kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>=</kbd> for superscript and <kbd>Ctrl</kbd>+<kbd>=</kbd> for subscript, but I can't use those since they trigger browser native zoom. Of course, I have separated buttons for super- and subscript and I will add hints to them, but I'd still like to make hotkeys as convenient as possible. Is there another common combination for these features?

Alternative Hotkeys

<kbd>Ctrl</kbd> + <kbd>.</kbd> for superscript and <kbd>Ctrl</kbd> + <kbd>,</kbd> for subscript are acceptable alternatives. (full stop / period and comma). They are the defaults set for Google Docs so familiarity will be reasonably high.

Accessibility Considerations

You cannot assume that any key is 'safe' as people may change their hotkeys to their preference.

For this reason you should always give people the option to change shortcut keys themselves in a settings menu (which should be easy to access).

You should also give people the option to toggle hotkeys on and off (yet again making the hotkey for that toggle customisable to their preference).

A lot of the time people come unstuck because they use a hotkey that overlaps with a screen reader hotkey and the hotkey doesn't work so make sure you consider the above before implementing hotkeys.

Also make it clear what hotkey is set for each item (to both sighted and screen reader users).