Multiple email accounts getting mixed up

Multiple email accounts getting mixed up

When I am in email with this new domain account, I will click on my calendar or contacts but sometimes they have no entries.

Then I find that Zoho has changed to a different account that I made months ago and am no longer using.  So I have to log out and in again in order to see my calendar and contacts.

So I tried logging in to that old account in order to delete it but while I was in the old account it switched back to the new account!

I've deleted cookies but it still happens.  The accounts keep getting mixed up.

How do I keep this new domain account and get rid of that old account?

Thanks!