USEINI

Using an environment variable:
E:\install\ZIEWin_pkgs\xxx\install\ZIEWin\setup.exe /v"/L*v 
	\"%temp%\pcsinst.log\" 
  USEINI=%ZIEWin_ini%\MyCustom.ini ONLYINI=1 TRANSFORMS=\"1033.MST\""

where xxx is mls.

Using UNC path names:
E:\install\ZIEWin_pkgs\xxx\install\ZIEWin\setup.exe /v"/L*v 
	\"%temp%\pcsinst.log\" 
  USEINI=\\MachineName\ZIEWin_ini\MyCustom.ini ONLYINI=1 
  TRANSFORMS=\"1033.MST\""

where xxx is mls.

The shared UNC path must have write access.