How can I change the registration email body of Webinars

You can not change the area you show. That is the "standard" answer of text produced by Zoom.
But if you look further down the email you will see 2 boxes where you can add text to the email.
One is before the connection settings and the second is after.

No. Just you need any one of the account that mentioned below.

Pro Account.

Business Account.

Education Account.

Enterprise account.

Confirmed, this can't be removed and is a small banner at the top of the emails. This seems to be rather new, as it was not there in the past. 

Looks like this in the email sent (I put a super oversized image on the branding banner just to see the scale).

It can be removable If you are an account owner or admin. Under account management->webinar settings->Registeration confirmation Email.

True, that can be done, but if you're going to point people to editing email code, it's best to offer them more guidance. 

 I'd have to spend more time with it to make sure it's just right. Then I'd need to do the same for every other email communication listed there if needed. It's a lot of effort and needs to be done properly and it will affect every webinar hosted on the account the action is taken on by every user. 

From some testing with the registration confirmation email, I was able to remove the following code from the email to remove the Zoom banner without obviously breaking anything.

Don't try this at home. 

________________________________________________________________
<tr>
<td style="vertical-align: top">
<table id="table-new-registration" border="0" cellpadding="0" cellspacing="0" align="center" style="width: 592px;">
<tr>
<td style="vertical-align: top;padding: 0px; background-color: #f4f5f9">
<table border="0" cellpadding="0" cellspacing="0" align="center"
style="margin-left: 0px;margin-right: 0px;width: 100%;background-color: #ffffff;padding-bottom: 37px;">
<#if zoomLogo?? && zoomLogo?length gt 0>
<tr>
<td style="padding-top: 30px;padding-bottom: 10px;background-color:#f4f5f9;text-align: center">
<a href="https://zoom.us">
<img src="${zoomLogo}" style="border-style: solid;" width="110" height="25" border="0"/>
</a>
</td>
</tr>
</#if>
<tr>
<td id="td1" style="padding-left: 28px;padding-right: 28px;">