python : jupyter lab 起動しません ImportError

Question

＜環境＞

1. windows10 64bit
2. anaconda3

＜起動手順＞
コマンドプロンプトにて以下のコマンドを実施
jupyter lab

＜結果概略＞
ImportError: DLL load failed while importing error:
が表示されて起動しない。

＜詳細＞
C:\Users\toshi>jupyter lab
Traceback (most recent call last):
File "C:\Users\toshi\anaconda3\Scripts\jupyter-lab-script.py", line 5, in <module>
from jupyterlab.labapp import main
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyterlab_init_.py", line 7, in <module>
from .labapp import LabApp
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyterlab\labapp.py", line 15, in <module>
from jupyterlab_server import slugify, WORKSPACE_EXTENSION
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyterlab_server_init_.py", line 4, in <module>
from .app import LabServerApp
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyterlab_server\app.py", line 7, in <module>
from jupyter_server.extension.application import ExtensionApp, ExtensionAppJinjaMixin
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyter_server\extension\application.py", line 21, in <module>
from jupyter_server.serverapp import ServerApp
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyter_server\serverapp.py", line 75, in <module>
from .services.kernels.kernelmanager import MappingKernelManager, AsyncMappingKernelManager
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyter_server\services\kernels\kernelmanager.py", line 19, in <module>
from jupyter_client.session import Session
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyter_client_init_.py", line 4, in <module>
from .connect import *
File "C:\Users\toshi\anaconda3\lib\site-packages\jupyter_client\connect.py", line 21, in <module>
import zmq
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq_init_.py", line 55, in <module>
from zmq import backend
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq\backend_init_.py", line 40, in <module>
reraise(*exc_info)
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq\utils\sixcerpt.py", line 34, in reraise
raise value
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq\backend_init_.py", line 27, in <module>
ns = select_backend(first)
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
mod = import(name, fromlist=public_api)
File "C:\Users\toshi\anaconda3\lib\site-packages\zmq\backend\cython_init.py", line 6, in <module>
from . import (constants, error, message, context,
ImportError: DLL load failed while importing error: 指定されたモジュールが見つかりません。

Answer 1

環境変数のpathに以下を追加したら起動しました。
C:\Users\toshi\anaconda3\Library\bin