[yencabulator]

The hollow zero vs slashed or dotted zero thing is often done in fonts with an extra variant; basically the font can contain both and will display what the application requests. So you should assume that the font really does have the slashed zero, but the font viewer you looked at it with didn't ask for it.

For web, https://developer.mozilla.org/en-US/docs/Web/CSS/font-varian...

[Zecc]

That's a good point. I added that rule (font-variant-numeric: slashed-zero;) to the font preview using the browser's devtools, and I saw no difference.