You can unlink the Google account from your Zoom account (I've done it succesfully) but it's rather convoluted process.
Let's say you currently log into Zoom using your Google account and you want to log in using your personal email account. Do the following steps:
Go to your Zoom account settings.
Find your current (Google) email and change it to your personal email. It's a long process and you need to confirm several emails when doing it.
After you complete this process, your Zoom email (used to receive emails from Zoom) will be your private email address but you will still have to log into Zoom using your Google account and you will have no Zoom password set!
Completely log out of Zoom website.
Click on "SIGN UP, IT'S FREE" to create a new Zoom user.
On the next page, enter your date of birth.
On the next page, enter your private email (not the Google email!).
Set a password.
This "new" Zoom user is automagically linked to your original Zoom account and you can now see "Linked Accounts: Google, Work Email" on your Zoom settings page.
You can now log into your Zoom account using your non-Google email and the password you set in step 8.
You can also still log into your Zoom account using your Google account. If you do not want this, you have to contact Zoom support and ask them to completely remove the "Google login" option from your Zoom account.