Granted it takes some force, but if you can get at least the left and the right side to pull away equally it will eventually give and come loose.

The result is a plastic case, housing the hard drive and electronics but thats easy to disassemble one you have removed the outer aluminum cover, as thats all it is. There is no other connection, even the holes for connectivity are just flush, they play no part in holding in the hard drive chassis.

In fact, if you like you can push the rubber feet through the aluminum case, as thats also part of the inner assembly. Just remember not to squeeze the aluminum case too tightly or malformed it as this in effect will just grip the internals even more making it even more difficult to remove.