I think I don't know how to explain what I'm having trouble with because that doesn't work either. In the video below I'm trying to get the boomerang to set its Z movement angle to the player throughout its entire return flight so it will home in on the player at the correct speed. If I can get this to work right then anything should be able to accurately aim at something in Z elevation.
It's using bullet behavior as well as a zAngle variable I made that alters its bullet speed so it moves the correct speed if aimed higher or lower. As you can see, the math is correct to change its movement based on zAngle as I can aim directly at the center of my vision no matter where I fire. The problem is that I set the zAngle to -3DCamera.CameraYRotation + 90 when the player fires to accomplish this, but I have no idea how to input something other than -3DCamera.CameraYRotation + 90 or a specific number which makes things like homing shots impossible until I know how. Thanks so far for the help though.
Here's a video attempting to show what I've done so far.
https://drive.google.com/open?id=1QurGjbN8Sn4EHbXZsv349R8_Ez19POBY&authuser=ummagummabur%40gmail.com&usp=drive_fs
EDIT: I found a diagram of the value I need to caclulate. It's X in this. Sorry if I'm being dense. This is actually the first time I've done anything in 3D. So I probably am like one of those 2D creatures in flatland coming into 3D. lol