Font size in TeXZilla rendering is much larger than the surrounding text

Math looks like this for me:

Math text is much larger than the surrounding text, and as a result inline formulas also align badly.

I looked in the Primary Styling CSS to see if there was any way to configure the size, but didn't find anything.

My font settings in Thunderbird are as follows:

I did also fiddle with the Mathematics font settings but that didn't make any difference.

I'm on a regular DPI monitor rather than a hi-dpi one.

The original MDH extension (eg in Firefox) uses a smaller font size although it's still larger than the surrounding text.