As you already know Zoom is a great tool for teaching and doing demos and sometimes having a bit of flexibility with choosing a different camera angle can be very handy.
Having a second camera can help get that angle that can help show what you are doing.
And then you are asking how to connect another camera. You can use your smartphone as well as other cameras. Below the video I have links to other videos showing you how to do this.
There are many uses for this including if you are teaching music, cooking, science, yoga, photography and many others where another angle would help. This doesn’t have to be just a close up but you could be more wide angle or just looking at it in a different way.
Depending on the camera and how easy it is to use then you can move it around. I do this with my smartphone. In fact if you look at the link below about using your iPhone as a document camera you will see I have a version that works on wifi which gives it a lot more freedom. That blog is not just about the document camera but being able to use it as a second camera too. Here is the link if you don’t want to scroll down, click here.
Here is a video I made. I use Zoom but this can work with other video calling software. If you want to use multiple cameras and switch quickly then have a look here at the blog I did about this great device called an ATEM Mini, click here.
Connecting a GoPro Hero 8 Black or Hero 9 (opens in YouTube)