Linear movement while easing speed 3D object in Z axis

[bend27845451]

I have some 3d extruded characters (numbers) that I want to float into the scene from a distance from different orientations coming to rest in front of the camera. The issue I'm having is that when I ease the Z axis so they come to a gentle stop, the characters start to curve out of the frame. I can't wrap my brain around how to maintain linear motion on the z axis, but change the speed of the character. I've included the video for reference. I need the 2 to come to a stop simultaneously with the 1 without swinging wide. Note - I don't know how I managed to get the 1 to do this, and when I copy it and try to change anything it no longer works. What am I not doing here!? Link to video: https://imgur.com/6OjIAHC

[Rick Gerard]

The only way I can think of to make the Z position of the second layer with the first layer is to open two views, look at the motion path from the top, and then use an expression to match the distance from the camera in Z to the second layer. The path's shape for the second layer must be managed by adjusting the motion paths' curve using the Top view.

This assumes the camera is at or close to its default X and Y positions. This simple expression will simply match the Z position of the second layer to the first. You'll have to edit the view:

refz = thisComp.layer(index - 1).transform.position[2];
[value[0], value[1], refz]

I don't have time to write an expression for you that matches the speed based on distance from the camera and takes into account and compensates for different ending distances from the camera. Just using two views makes it pretty easy to adjust the timing and path of two different layers. If I get a chance, I'll fiddle with the distance from the camera approach later this evening. 

[bend27845451]

Thanks for the advice!