If the overlay is set at the start of the scene, drop the “shifts to”. So:
INT. BACKGROUND with OVERLAY NAME to 1.000 0 0 in zone 1 at layer 2"
If the overlay is set later in the scene, just break it up to:
&overlay OVERLAY NAME shifts to 0 0 in zone 1
&overlay OVERLAY NAME moves to layer 2
I believe you can only use “at layer” if it’s set with the background at the beginning.