Either this doesn't change to scoreboard score or it is not displaying the change from the score
To my understanding this should set any zombie with a rotation minimum of 88 and a maximum of 90 to a score of rotation equals 90
Sorry I typed the command in wrong to this comment. It is execute @e[type=Zombie,rym=88,ry=90] ~ ~ ~ scoreboard players set @e[c=1] rotation 90
More specifically execute @e[type=Zombie,ry=90] ~ ~ ~ scotreboard players set @e[c=1] rotation 90
This is also a problem in 1.8.3
Should @e select the closest entity executing the command? There for the zombie executing the command?