This is a very old issue, it's been around probably as long as there's been a battle camera (but I searched and couldn't find it in the Archives)
While in battle, using the scroll wheel to change the camera zoom also scrolls the chat window, making it difficult to talk with others on a server. For example, if you zoom in, you might scroll up to the top of the chat history; then if you try to catch up in chat you'll end up zooming really far out.
Ideally the chat window should only scroll when you hold your pointer over the chat window - and in any location outside that window, it should zoom the camera. If that's not possible, maybe add a button to lock the camera in place once you're finished moving it? Idk, there must be some way to control these two things independently.