make fake hole, vfx graph and depth mask issues

Hello,

i try to make an effect to have fake “space hole” in any another mesh, terrain especially.

actually, i have this kind of thing:

to make this i have a crack top plane mesh with this shader to make a mask on mesh which have hole

Shader "Custom/DepthMask"
{
    SubShader{
        // Render the mask after regular geometry, but before masked geometry and
        // transparent things.
        Tags {"Queue" = "Geometry+10" }

        // Don't draw in the RGBA channels; just the depth buffer
        ColorMask 0
        ZWrite On

        // Do nothing specific in the pass:
        Pass {}
    }
}

and a small crack down mesh beside this mask with layer “Nothingness”, decorated with animated shader (shader graph) which represent space in hole
i also have a layer “AboveNothingness”

so i have 2 render objects in my universal renderer data asset, as described in URP doc tutorial (Example: How to create a custom rendering effect using the Render Objects Renderer Feature | Universal RP | 13.1.9) to render some objects on top of the nothingness

On top of that i have a VFX graph to generate some particles which must go in space hole
but theses particles rendering are graphically cut and hidden by crack top mask mesh and crack down mesh as you can see in first and third capture

please, how i can achieve my goal ?
maybe there is a better and approach to do all of theses things ?
i’m not really advanced in shaders and rendering.

Does anybody have an idea how to achieve that ?