What is wrong with this command?

/summon minecraft:zombie 181.5 64 611.5 {CustomName:"General Zombo",CustomNameVisible:1,Attributes:[{Name:"generic.maxHealth",Base:100d},{Name:"generic.knockbackResistance",Base:1d},{Name:"generic.movementSpeed",Base:0.25d}],Health:100f,HandItems:[{id:"minecraft:diamond_sword",Count:1,tag:{Unbreakable:1}}],ArmorItems:[{id:"minecraft:iron_boots",Count:1,tag:{Unbreakable:1}},{id:"minecraft:iron_leggings",Count:1,tag:{Unbreakable:1}},{id:"minecraft:iron_chestplate",Count:1,tag:{Unbreakable:1}},{id:"minecraft:iron_helmet",Count:1,tag:{Unbreakable:1}}],Tags:["boss1"]}

Minecraft just gives me an extremely unhelpful "unable to summon entity". I'm not very experienced with complex summon commands and have no idea what I did wrong.