I assume you don't want a full screen reader if you're not already using one, but if toasts are properly implemented (big if), screen readers can actually present them accessibly via the ARIA alert pattern[0].
Wanted to mention in case you're not aware and maybe there's some tool somewhere (or some way to configure a screen reader?) so that you can keep your simple zoom workflow but still benefit from the ARIA alert pattern.
Thanks for this! I visited your link and hadn’t seen such a nice demo with working code on w3.org before: whoever worked on these pages deserves kudos.
Wanted to mention in case you're not aware and maybe there's some tool somewhere (or some way to configure a screen reader?) so that you can keep your simple zoom workflow but still benefit from the ARIA alert pattern.
[0] https://www.w3.org/WAI/ARIA/apg/patterns/alert/