here is an example:

        devShells.default = (pkgs.mkShell.override { stdenv = stdenv';}) {
          nativeBuildInputs = buildDevToolsDeps ++ buildToolsDeps ++ shellTools;
          buildInputs = buildDeps ++ testDeps;
          shellHook =
            ''
              BUILDER= ZDOTDIR=${zshDir} zsh -d && exit
            '';
        };

        # This shell is gcc based and we use it only
        # for the mathematics side of our design
        devShells.math = nativePkgs.mkShell {
          #nativeBuildInputs = mathDeps;
          buildInputs = mathDeps;
          shellHook =
            ''
              BUILDER=Math ZDOTDIR=${zshDir} zsh -d && exit
            '';
        };