Nice! Will anything need to be changed to compensate for the larger tires?
To use the Maxxis tires you'd use their 120/70-12 tire on both front and rear (they're not position-specific, so no issues there). Maxxis doesn't currently make a 100/90-12 tire in the M6024's.
Going up in size to the 120 on the front would have minimal effect, the differences in dimensions are small except for width. The 120 is about 3/4" inch (20mm) wider. Once you have your Z, just make sure that there is at least 20mm extra room between the forks on each side of the stock tire for clearance. You'd only need 10mm (1/2 the total 20mm extra width) extra clearance on each side to fit the new tire (it would touch the forks if that was all the room there was) so 20mm on each
side is better and would give you a buffer since the tire gets wider when it flexes, particularly over bumps. That way it wouldn't rub on the forks when flexing.
Here are charts showing differences between the two front tires:
You can ignore the speedometer reading difference chart since you wouldn't be changing the rear tire size. Speedo would read same as with stock tires, which is usually about 7-10% high compared to actual speed. You can use your smartphone and a speed app to find actual speed on the road.