Welcome to the forum. There's several different ways to accomplish the movement.
You could have a repeat forever loop in the zombie:
Set Position to x: Zombie_X_position + (Hero_X_position - Zombie_X_position)/Abs(Hero_X_position - Zombie_X_position) * Step_Size
repeat the formula for the y:
Make the Step_Size however far you want it to move with each loop.
Note that this has a couple draw backs.
1. The step_size controls the apparent speed. You can't use Set Speed
2. The formula results in a faster apparent speed (1.414 times faster) as the direction approaches 45 deg (in any of the 4 quadrants)
Make When 7=7 (which is another way of making a repeat forever) in the zombie with:
move forward (100)
Make another When 7=7 with:
Theta = arctan((Hero_Y_position - Zombie_Y_position)/(Hero_X_position - Zombie_X_position))
If Zombie_X_position > Hero_X_position
Increase theta by 180
Set Angle (theta)
Where Theta is a variable that you'd make.
In a When Game Starts for the Zombie, set the speed that you want (or change it at any time)
Note: this also has a draw back that the character doesn't stay "right side up" if that's what you had wanted.
Good luck & have fun! Tag me with questions. There's still more options if the above don't meet the specific needs of a given project.
P.S. There's no such thing as a dum.b question. Never worry about that! Asking questions is the process by which we all individually learn.