Addition to Standard Shader stopping it from batching?

I added the following code to the start of the Standard Shader:

         Pass 
         {
             ZTest Always 
 
             ColorMask 0
             ZWrite On
         }

This is designed to clear the z-buffer behind this object - enabling me to have control over which objects render in which order. The problem is it gives me issues with batching. If I drop a ton of cubes into the scene with a material with the regular Standard Shader then it's a fixed number of draw calls - no matter how many cubes I have. The second I add that excerpt to the shader, that scheme breaks! Adding more cubes adds more draw calls, is something wrong or is that a necessity with this snippet of code?