Neither setting is needed on any reasonably modern hard drive, if it is the
drive's documentation or label will tell you so.  But to directly answer
your questions:

WRITE PRECOMP is the cylinder number at which the electrical current for the
drive head changes to compensate for differences in data density across the
disk surface

LANDING ZONE is where the drive head should be parked when powered down.

Write Precomp:
(Write Precompensation) Older hard drives have the same number of sectors per track
at the innermost
tracks as at the outermost tracks. This means that the data density at the innermost
tracks is higher and
thus the bits are lying closer together. Starting with this Cylinder until the end
of Cylinders the writing starts
earlier on the disk. In modern HDs this entry is useless. Set it either to -1 or max
Cylinder (a common value is
65535). For IDE hard drives it is not necessary to enter a WP cylinder.  The IDE HDD
will ignore it for it has its own parameters inboard.

Landing Zone:
The address of the landing zone. Used in old HDs without an auto-parking feature, or
RLL. Set it to 0 or
max Cylinder.