Formatting a disk just replaces the beginning of track marks and initializes the FAT. Zero filling overwrites everything and makes it almost impossible to recover data even with more sophisticated equipment. When you format the disk, all of the old data is still there, it's just not readily accessable since the FAT does not "point" to the disk location any longer. You could still perform a disk "absolute address" read and extract the data.
Zero. In general, the difference between any number and itself is zero.
There is no difference in value between "equal" fractions: the difference is zero.
infinite
zero
Nought is just another word for zero.
the difference between two equal fractions is zero.
The difference between anything and itself is zero.
Zero.
the difference is that one is the letter o and the other is a zero
Zero
Zero.
Zero