  We apply symmetry considerations to study the possible superconducting order
parameters in ferromagnetic ZrZn_2. We predict that the presence and the
location of the superconducting gap nodes depend on the direction of
magnetization M. In particular, if M is directed along the z axis, then the
order parameter should always have zeros. We also discuss how to determine the
gap symmetry in ZrZn_2 using ultrasound attenuation measurements.
