I remeber something like this for someone else a while back and it seems this worked for them.
zsh-256color is not a plugin but rather a terminal capability related to color support.
I suggested to enable 256-color support in Zsh is to ensure the TERM environment variable is set to xterm-256color in your shell configuration file, such as ~/.zshrc
That should fix the rest as well.
To make clear use, export TERM=xterm-256color in your ~/.zshrc