In researching how to remove the Zoom header and footer from a Webinar registration page for a clean embed on our website, I found this thread.
There are a lot of soutions on there, but all I had to do was edit the custom CSS from the Advanced > Branding tab in an Admin account to hide the containers as such:
.branding #header .logo {
display: none !important;
}
#header .action-btns {
display: none !important;
}
#footer_container {
display: none !important;
}
#header_container {
display: none !important;
}
The first two might be unnecessary with the containers being hidden by the following two, but I was going back and forth with our admin over Slack and left it as such because it worked.