How to merge meshes from gltf file and instance them?


I want to use instances with the following GLTF in order to display a lot of it. The problem is that the GLTF is composed of 2 geometry and 2 different material. I have looked at the “merged” function from R3Drei but I’m not sure I can then instantiate the mesh in order to display several of them.
How can I merge those mesh in order to instance them with for example “Instances” from R3Drei?

const Axe = ({ scale, ...props }) => {
  const { nodes, materials } = useGLTF(axeUrl)
  return (
    <group  dispose={null} {...props}>
      <group rotation={[0, Math.PI / 1.8, -0.3]} scale={scale}>
        <mesh geometry={nodes.Mesh_1001_1.geometry} material={materials.material_2} />
        <mesh geometry={nodes.Mesh_1001_2.geometry} material={materials.material_3} />