I am looking for a script solution to merge all layers to layer 0.
First I unlock all layers and switch to layer 0.
My srcipt looks like this:

(defun c:lm0 ()
(command "._LAYER" "_UNLOCK" "*" "")
(command "._LAYER" "_THAW" "*" "")
(command "._LAYER" "_ON" "*" "")
(command "._LAYER" "_ON" "0" "_UNLOCK" "0" "_THAW" "0" "S" "0" "")
(command "._LAYMRG" "N" "*" "" "N" "0")
(princ)
)
Problem is that -laymrg will not accept * to select all layers.
How can you do that?

You may have to do something like this, where you iterate the layer collection, feeding each layer name into the LAYMRG command.



Code:
(vlax-for
x
(vla-get-Layers (vla-get-ActiveDocument (vlax-get-acad-object)))
(command "._laymrg" "_N" (vla-get-Name x) "" "_N" "0" "_Y")
)