zsh:tldr:e35a5

The command "${echo Hello world} | zsh" consists of two parts: "${echo Hello world}" and "zsh".

The part "${echo Hello world}" uses the command "echo" to output the string "Hello world". The "$" symbol is used to indicate that what follows is a command substitution, meaning the output of the command "echo Hello world" will be substituted in place of "${echo Hello world}".

The "|" symbol is known as a pipe and it is used to redirect the output of one command as the input to another command. In this case, the output of "${echo Hello world}" is piped (or passed) to the "zsh" command.

The "zsh" command refers to the Zsh shell, which stands for Z Shell. It is a Unix-like command interpreter and interactive login shell. When the output of "${echo Hello world}" is piped to "zsh", it means that the Zsh shell will receive the string "Hello world" as its input.

Overall, this command will execute the "echo" command to output the string "Hello world", and then pass that output as input to the Zsh shell.