The zombie meshes have extra variation options available as BlendShapes

These vary depending on the used base mesh but allow you to tweak things like hair and fatness among other things

The Blendshapes area available on the mesh object within the zombie prefab.

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Sleeve and Trousers will be useful when the texture represent long/short sleeves or long/short trousers.

These variations can be applied on each prefab instance or to the prefab itself if needed.