Which letter has rotational symmetry?

P

Z

W

F

Z has rotational symmetry. It looks the same rotated 180 degrees.

Test each letter:

P rotated around looks something like d, so no;

Z rotated around is still Z, so yes;

W upside down is M, so no;

F upside down is something like

|

__|

___|

So no. The correct answer is Z.