The system folder is not blessed on that media, which is why your System 7.5.x is not loading. Usually if the system enabler is missing, you get the Smiley Mac and then an Error Window saying "This System is not for this Mac."
Booting from a Zip Drive is difficult as not all systems will boot off it (the LC 475 should however). The cartridge needs to be Mac formatted on the Mac and the System put on it first and then blessed. A PC Formatted cartridge will be readable but not bootable.
I forget where, but there are sites out there, including Apple, where you can download the proper System Enabler for the LC 475. This is why I prefer System 7.6, it does away with System Enablers.
Booting from a Zip Drive is difficult as not all systems will boot off it (the LC 475 should however). The cartridge needs to be Mac formatted on the Mac and the System put on it first and then blessed. A PC Formatted cartridge will be readable but not bootable.
I forget where, but there are sites out there, including Apple, where you can download the proper System Enabler for the LC 475. This is why I prefer System 7.6, it does away with System Enablers.