No, you cannot use a 7-1/4 inch blade on your Makita XSH03Z. The tool is specifically designed and guarded for a 165 mm blade, which is 6-1/2 inches.
Using a larger blade will affect the operation of the lower guard. The guard will not close properly over the larger blade, leaving it exposed, which creates a direct risk of serious injury.
The blade must also have the correct size and shape of arbor holes to match your saw's mounting hardware. A blade that doesn't match will not mount correctly, run eccentrically, and cause a loss of control.
You must use a sharp, clean 165 mm (6-1/2") blade meant for this saw. This is a critical safety requirement built into the tool's design.