Likely these:
public static Item Iron_Synthesis = new ModSynthesis(911, "Iron_Synthesis", EnumToolMaterial.Synthesis_IRON, 0).setUnlocalizedName("Iron Synthesis");
public static Item Gold_Synthesis = new ModSynthesis(912, "Gold_Synthesis", EnumToolMaterial.Synthesis_GOLD, 0).setUnlocalizedName("Gold Synthesis");
public static Item Diamond_Synthesis = new ModSynthesis(913, "Diamond_Synthesis", EnumToolMaterial.Synthesis_EMERALD, 0).setUnlocalizedName("Diamond Synthesis");
The problem is that he didn't change/override/include in his release zip EnumToolMaterial