Shell Programming and Scripting

I have a question of how to run commands from a variable where there are more than one commands in the variable under bash.

I ran the following commands under bash

> command="ls /etc/zshrc; ls /etc/zshenv"
> $command

The results were:
ls: /etc/zshrc;: No such file or directory
ls: ls: No such file or directory
/etc/zshenv

But, when I ran this command:
> eval "$command"

The command yielded the right results:
/etc/zshrc
/etc/zshenv

Why $command didn't work?

Thanks.

Because by the time that a variable is expanded, some other processing has already been done. Now you that processing to happen a second time. That's what eval does.