The ZED cameras are passive depth sensors. This means that it doesn't emit any laser or IR light like active sensors.
Multiple passive sensors can be used at the same time without any kind of interferences and as they are not using IR light, they don't suffer from sunlight interferences.
Active sensors are also focused on a much smaller range for technical reasons, while the ZED can measure depth value at very high ranges. (Depth range of the ZED2 and ZED2i is 20m in 3D and up to 40m in 2D)
Another advantage is the image and depth alignment. As the depth is computed from the images, the left image and the depth map are perfectly aligned and you can use the same pixel coordinate in both of them to target the same object.
With the ZED SDK, you can have access to all the features such as object detection, skeleton tracking, spatial mapping, positional tracking for SLAM(Simultaneous localization and mapping).
Another advantage of the ZED stereo camera can be a high resolution and frame rate compared to the active sensors.