Hi there,
There can be multiple approaches to this.
Q1: You don’t really need Z Depth to achieve that effect. You can just scale it down and when its masked it will appear to be in Z Depth. You can use 2 sub widgets in one container widget : let’s say HUDContainer, Display1_WGT, Display2_WGT..
Q2: Animation is the tricky part of this, since the animation should be always parallel to the road. So you have to know where the road is while doing the animations. Even though from my perspective this would be not appearing the best through ScreenSpace UMG… However if its not AR but static on windshield, it can be done nicely if the widgets are static you can always mask the one behind. For masking you can check UE Retainer Box Mask
If this is AR you can use the other features of the engine like WidgetComponents for actors. You can create 2 actors with widget components. Make animations in real 3D AR and umg only does masks and display required data. (I would have gone this direction)