I have elite zumo in hand. and very loud. This sound is like the sound of a tractor … I went where I bought it. did not find a problem. pedals that I am officially driving the tractor … 
I wrote to elite spport, waiting for an answer
My Zumo is very quiet. There’s clearly something wrong with yours. I’m sure that Elite support will help you to sort it out.
I think there is a problem. I am adding a video but the forum does not accept
If you’ve only just bought it, can you not get the seller to replace it?
I bought it in september 2020. There was this problem in the beginning.
I’m throwing a video link. from google drive but not working
I’d only suggest this IF it’s out of warranty because they will fix this under warranty.
My Zumo has done this twice, if it sounds like something rubbing, it’s the internal belt rubbing off the internal cams.
To fix it, simply take the 8-10 screws off of the plastic work, remove the cover and check if the belt has slipped. If it has, move it back into place.
I found that oiling my chain was the problem (I never oil it while on the TT now). Made it into the internals and caused the belt to slip.
Be carful, because the cams are sharp, if you continue to ride with this problem it will damage the belt. Best fixing straight away. First time it happened, my belt snapped.
Hasn’t happened since I stopped oiling the chain on the TT (over a year ago).