Zack Khan has 1.5 inches bigger arms. But he is taller so it's only natural.
...based on his bodyweight and height, Zack Khan has arms maybe half an inch to three quarters of an inch bigger.
The pics of his arms taped show that too.
Remember, you need to add a muge amount of bodyweight to increase an inch when your arm is already over 20 inches.
The guideline weight for a 21'' arm is 294 lbs (assuming average height and 10% bf)
The guideline weight for a 22'' arm is 323 lbs
The guideline weight for a 23'' arm is 353 lbs
Zack Khan's arms are just over 22''... but that's still a full 7% bigger than Heaths (and there just so happens to be a 7% difference in their lean bodyweights too).
The Luke