That would be the only mower that has this set up
Every other mower I have worked on, around 5000 or so, the smaller pulley is the transmission & the pulley stack has it on top .
Was this mower bought new or used ?
I can not find a parts breakdown for a zkw2560 , the closest I can find is a ezkw2352
Now the exploded parts diagram is printed upside down , and it shows the drive pulley above the clutch pulley remembering that the top of the image is the bottom of the mower ( note the position of the lap bars )