How to force two objects to render.

Hi, New to game development and hit my first snag after 3 weeks.

I thought I'd be clever and a 3D position marker for my 2D game. The marker has an up-down set of arrows at z = 0 and a left-right set of arrows at z = -1. When looking in 2D you just see four arrows as desired. A second marker in a different colour is rotated 90 degrees in the z axis. I desired that when the position markers are at the same coordinates I would see one colour pointing up-down and the other colour pointing left-right so the user would see a part of each marker. However unity renders one object completely over the top of the other.
How can I make the parts of the both objects closest to the camera appear similtaneously? Ultimately I want to animate both markers spinning together in the z axis.

Photos included for clarity with 2D view on the bottom.