Ecamm Live's Virtual Camera and the Sharing Window features are both a great way to send a video stream from Ecamm Live to Zoom.
Ecamm Live's Virtual Camera feature presents itself as a 1080p camera source in apps such as Zoom. Note however that Zoom will not usually broadcast camera sources in 1080p. Ecamm Live does not have the ability to increase the quality of a Zoom video feed. Zoom quality is dictated by a variety of factors includes internet speed, your Zoom plan, and current network usage.
This means that your Zoom guests may not see the same quality that you see in Ecamm Live. This especially noticeable when using Ecamm Live's screen sharing feature to present your Mac's screen. If quality is not high enough, we recommend using Zoom's screen sharing feature rather than Ecamm Live's Virtual Camera.
For more information on this topic, we recommend reading through Zoom's support documentation on this topic.
In Zoom's Video preferences, ensure that the "Enable HD" option is selected.