How do I find the distance between two gameobjects just on the x axis?

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C#

I am made rows for each gameobject that I spawn in to go down and if they are within range of an enemy, they will attack that enemy and then keep going. But the rows are close so if I have the range of the Gameobject too big then they will attack the other enemies in the rows next to them once they come within range. If both players are in the same row they have the same z position and so what I want to do is, if they have the same z position, they can attack each other, if not, then they can't attack.

What I have tried:

float distanceToEnemy = Vector3.Distance(transform.position, enemy.transform.position);

thats what I tried for getting the distance and it works, its just I want it to be more of a box range rather than a sphere range.

if (nearestEnemy != null && shortestDistance <= range && transform.position.z == nearestEnemy.transform.position.z) {
			target = nearestEnemy.transform;
			inRange = true;
		} else {
			target = null;
			inRange = false;
		}

and thats what I did to make the player shoot only the enemies that have the same z position as it, but it didn't work, or doesn't work all of the time