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You can't upgrade from the settings. For this, You need to use the Zorin OS Upgrader Tool. You can install it in the Terminal with sudo apt install zorin-os-upgrader
Because of Your Modifications it depends what You have done. Gnome Extensions could be a Problem when they are not compatible with Gnome 43 from the Zorin 17 Core Desktop. So, I would suggest at least to turn them off. The same with Themes. And when You have added third-party PPA's (and the Software of these), it would be good to disable them, too.