In an Sega Saturn Magazine interview, the game's planner Koji Okohara stated that looking back at Mega Man X3, they felt there wasn't a big enough difference between how Zero and X controlled, so they tried to distinguish both of them further in the sequel. In X4, Zero only got a sword without any "charge" ability for his weapon.

The game's producer Yoshinori Takenaka stated that many developers were against that decision. Koji Okohara also stated "His sword doesn’t have any reach, and they thought it would make the game too difficult. To address that, we raised his attack power and added Street Fighter-style moves, so he feels completely different from X."
Contributed by ProtoSnake