以下、条件を満たすecsタスクを探す時に使用したshell script

#!/bin/bash
clusters=$(aws ecs list-clusters | jq -r '.clusterArns[]')

for cluster in ${clusters}; do
  echo "====================="
  echo "===cluster==="
  echo $cluster
  tasks=$(aws ecs list-tasks --cluster $cluster | jq -r '.taskArns[]')
  echo "===tasks==="
  if [ -n "$tasks" ]; then
    echo $tasks 
    echo "===target==="
    for task in ${tasks}; do
      target=$(aws ecs describe-tasks --cluster $cluster --tasks $task --query 'tasks' | jq '.[] | select(.availabilityZone == "ap-northeast-1a")' | jq '.clusterArn')
      if [ -n "$target" ]; then
      	echo $target
      fi
    done
  else
    echo "no task in $cluster"
  fi
  echo "====================="
done

以下部分をアレンジすれば条件に合ったecsタスクの情報を取得できます。

select(.availabilityZone == "ap-northeast-1a")' | jq '.clusterArn'