How do I give an achievement to a player if he killed a zombie named test?

Here's what I have.
{
    "display": {
      "icon": {
        "id": "minecraft:player_head"
      },
      "title": {
        "text": "Амадеус",
        "color": "aqua",
        "obfuscated": true
      },
      "description": {
        "text": "Ейфвщй кхрфі г жчф збгбрщфі ойгійр трхої ь ойлммл тлбдій",
        "color": "dark_purple"
      },
      "frame": "challenge"
    },
    "parent": "main:legendary/root",
    "criteria": {
      "t": {
        "trigger": "minecraft:player_killed_entity",
        "conditions": {
          "entity": {
            "type": "minecraft:zombie",
            "nbt": "{CustomName:'{\"text\":\"test\"}'}"
          }
        }
      }
    }
  }