If a plugin cancels the EntityTransformEvent event, the equipment on the original entity will be lost as it goes to the transformed entity.

How to reproduce:

1. Run a test plugin with the following code:

   @EventHandler
   public void onEliteTransform(EntityTransformEvent event) {
       Bukkit.getLogger().info("Cancelled EntityTransformEvent for " + event.getEntity().getName());
       event.setCancelled(true);
   }
   

2. Run this command in the console:

   give @p zombie_spawn_egg[entity_data={id:zombie,DrownedConversionTime:20,HandItems:[{id:diamond_sword,count:1},{id:shield,count:1}],ArmorItems:[{id:diamond_boots,count:1},{id:diamond_leggings,count:1},{id:diamond_chestplate,count:1},{id:diamond_helmet,count:1}],HandDropChances:[0f,0f],ArmorDropChances:[0f,0f,0f,0f]}] 1
   

3. Spawn the Zombie

Observed Results:
The Zombie lost its equipment. You can see that it went to the transformed entity by doing:

EntityEquipment equipment = ((LivingEntity) event.getTransformedEntity()).getEquipment();
Bukkit.getLogger().info("ArmorContents: " + equipment.getArmorContents());
Bukkit.getLogger().info("ItemInMainHand: " + equipment.getItemInMainHand());
Bukkit.getLogger().info("ItemInOffHand: " + equipment.getItemInOffHand());

Expected Results:
The Zombie keeps the equipment since the event was cancelled.