Integrations can be dual run, so you could set up a new integration for Google Workspace or Microsoft 365 while retaining the original integration.
This is helpful if you want to ensure no impact to employees logging in.
You can manage integrations by going to System Config > System Integrations.
Here you can enable the new integration and disable the old.
If employee emails are changing, this is all you need to do.
If you're changing employee email addresses, then you will need to disable the original integration to make the email address field editable.
Then go to Organisation > Employees and edit the email addresses.
Finally, head back to System Config > System Integrations to enable the new integration.