Why is my vertical movement faster than my horizontal?

My PlayerController.cs code:

 using UnityEngine;
 
 [RequireComponent(typeof(Rigidbody2D))]
 public class PlayerController : MonoBehaviour
 {
     Rigidbody2D rb2d;
     bool isMoving;
 
     public float moveSpeed = 500f;
 
     private void Start()
     {
         rb2d = this.gameObject.GetComponent<Rigidbody2D>();
     }
 
     public void Move()
     {
         float moveX = 0;
         float moveY = 0;
 
         // Only let player moves when they are not moving
         if (isMoving == false)
         {
             moveX = Input.GetAxisRaw("Horizontal");
             moveY = Input.GetAxisRaw("Vertical");
         }
 
         if (moveX != 0 && moveY != 0)
         {
             // If player tries to move diagonally, return nothing
             return;
         }
 
         if (moveX != 0 || moveY != 0)
         {
             Vector2 moveVelocity = new Vector2(moveX, moveY).normalized * (Time.deltaTime * moveSpeed);
             rb2d.velocity += moveVelocity;
             Debug.Log(rb2d.velocity);
             isMoving = true;
         }
 
         if (rb2d.velocity.x == 0 && rb2d.velocity.x == 0)
         {
             isMoving = false;
         }
     }
 }