Not an “easy” way, but what I’ve been doing is simply whenever I handle an email in the account I want to switch from, I use that particular situation to change the email in the settings of the account of whatever I’m handling in that moment.
That way it doesn’t become an overwhelming task, and if you are consistent with it and do it each time you handle an email, slowly but surely you will have switched completely.
Not an “easy” way, but what I’ve been doing is simply whenever I handle an email in the account I want to switch from, I use that particular situation to change the email in the settings of the account of whatever I’m handling in that moment.
That way it doesn’t become an overwhelming task, and if you are consistent with it and do it each time you handle an email, slowly but surely you will have switched completely.