Zoom does have an in-built echo removal. But sometimes this does not remove the high-pitched feedback that can occur between your microphone and speakers. Therefore, have a tested pair of headphones available.

Zoom provide a test meeting: https://zoom.us/test

If you have not used Zoom before on your current PC setup, please visit the zoom test meeting and check that everything works.

Dress as if in a physical meeting; from head to toe.

Don’t use a distracting background within Zoom. These are alot of fun for a social event, but can be distracting for presenters and other attendees.

See: https://www.psychologytoday.com/us/blog/do-the-right-thing/202003/top-10-tips-good-zoom-hygiene-and-etiquette-in-education

A good article on body language while being viewed on a webcam:

https://www.fastcompany.com/90501804/body-language-is-important-even-on-zoom-here-are-4-ways-to-improve-yours