I hear my voice echo

What audio device is your teacher using? Do they have original sound for musicians on?

Then it sounds to me like his soundboard that is receiving your voice is also sending it back out to zoom so you have slapback. When original sound for musicians is on zoom does not process any audio so it will not get rid of that slapback. What he needs to do is turn on mix minus on his mixer, what this does is anything coming in on that channel does not get sent back out to the zoom meeting. Depending on the mixer this is really easy to do

I will explain this to him and let you know if it works.

thank you!