(¬x→z) • (x→¬y•z)=(xvz) • (¬xv¬y•z)=x•¬xvx•¬y•zv¬x•zv¬y•z•z=
=0vx•¬y•zv¬x•zv¬y•z=x•¬y•zv¬x•zv¬y•z= ¬x•zv¬y•z
(¬x→z) • (x→¬y•z)=(xvz) • (¬xv¬y•z)=x•¬xvx•¬y•zv¬x•zv¬y•z•z=
=0vx•¬y•zv¬x•zv¬y•z=x•¬y•zv¬x•zv¬y•z= ¬x•zv¬y•z