In a Vanilla Minecraft server, zoglins will find a new target after their first target is killed, which is the expected behavior, but on a Spigot server, zoglins won't find a new target after their first target is killed by the zoglin or by the player. The zoglin will remain passive to all mobs unless attacked by the player or another mob, in which case the zoglin will attack that player or mob until death, but afterwards it will go back to being passive.

Steps to reproduce:

1. Spawn in a zoglin with a spawn egg
2. Spawn in any mob except a creeper or another zoglin.
3. The zoglin will target and attack that spawned in mob until it dies.
4. Again, spawn in any mob except a creeper or another zoglin.
   1. In a Vanilla Minecraft server, the zoglin will target and attack that spawned in mob.
   2. In a Spigot server, the zoglin will not target any other mobs unless attacked.