Copying the contents of the folder is the correct way. I have a mac as well and when you decompress the ML zip, it makes a new folder named the same as the zip. What you need on the card is a ML folder, the .fir files, and autoexec.bin
When you installed the 2.1.2 firmware, did you format the card afterwards before putting the ML files on it? You definitely don't want the Canon firmware files on the card at the same time as the ML .fir files.