What is the difference between zImage and bzImage targets when compiling a kernel?

What is the difference between zImage and bzImage targets when compiling a kernel?

A.
zImage is compressed using gzip, bzImage is compressed using bzip2

B.
zImage is for 2.4 series kernels, bzImage is for 2.6 series kernels

C.
zImage is loaded into low memory, bzImage is loaded into high memory

D.
zImage is limited to 64k, bzImage is not