I cant summon a wither skeleton with enchanted armor

you can use this summon generator to summon a wither skeleton or any other mob https://minecraft.tools/en/spawn.php

or here is a command for summon a very powerful wither_skeleton you need to use a command block /give @p minecraft:command_block 1

summon minecraft:wither_skeleton ~ ~1 ~ {CustomName:""king"",CustomNameVisible:1,PersistenceRequired:1b,LeftHanded:0,Health:100,Attributes:[{Name:"generic.maxHealth",Base:100},{Name:"generic.followRange",Base:500},{Name:"generic.knockbackResistance",Base:1f},{Name:"generic.attackDamage",Base:10}],HandItems:[{id:"minecraft:diamond_sword",tag:{display:{Name:'{"text":"die"}'},Enchantments:[{id:sharpness,lvl:5},{id:knockback,lvl:2},{id:fire_aspect,lvl:2}]},Count:1},{}],ArmorItems:[{tag:{Enchantments:[{id:protection,lvl:4},{id:feather_falling,lvl:4},{id:thorns,lvl:3}]},id:"minecraft:diamond_boots",Count:1},{tag:{Enchantments:[{id:protection,lvl:4},{id:thorns,lvl:3}]},id:"minecraft:diamond_leggings",Count:1},{tag:{Enchantments:[{id:protection,lvl:4},{id:thorns,lvl:3}]},id:"minecraft:diamond_chestplate",Count:1},{id:"minecraft:diamond_helmet",Count:1,tag:{Enchantments:[{id:protection,lvl:4},{id:thorns,lvl:3}]}}],ActiveEffects:[{Id:8,Amplifier:0,Duration:2147483647}]}