Ah, yes. Well, there's a bit of politics involved here....
Canonical, the company that develops the Snap package format, made the decision to replace certain software from their repositories with their respective Snap versions. Firefox being one of the most notorious examples, and was seen as a very controversial move.
Since Zorin OS is based on Ubuntu (Canonical also develops Ubuntu) it's finding it that way. You can verify this is you search for Firefox on the terminal:
You probably read about don't use Snap because it has been recently in the news due to some vulnerability. In general, it seems that Flatpak is more mature, although I still prefer to use the native format whenever possible.
As for Firefox I don't really know how well does the Snap version work, you can try it if you like, but if you want to avoid this situation you have a couple of options:
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Remove Snap entirely from your system. This is entirely up to you but if you don't use other Snap packages it's probably best.
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Install Firefox directly from Mozilla (company behind Firefox). As they've recently released a repository for this purpose it may be a good solution if it's the only non-Snap package that you want installed.
By default, starting with Zorin OS 17, Firefox comes preinstalled as a Flatpak package.