It's not a good idea to call a macro from another macro in Mach3. The chances of it not working correctly are very high. If you really want to try it, the code for your auto zero macro is probably embedded in the button. In Mach3, go to Operator, Edit Button Script and click the Auto Zero button. You should see the code open in the editor. You'll want to save this as a standalone macro in the macros folder. You'll need to look in the programmers reference manual to find the command to call a macro from within a macro. I don't know what it is off the top of my head.