A For Mazda 3 2004-2005, you can refer to this method to modify your car to retain the factory car LCD screen: http://www.mazda3forums.com/showthread.php?t=387058
For Mazda 3 2006-2009, Eonon car stereo can be compatible with the factory car LCD screen without modification. How to use it: https://www.youtube.com/watch?v=P0suhaVKObQ