I have rvm installed on my machine even before I start using ohmyzsh. I ‘ve decided to make a switch because of its plugins and aliases. However, after I install zsh, my rvm is totally wracked. After days and days of trying to figure it out, I found the fix. All I had to do is to add this code below to ~/.zshrc

[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" 

Woo hoo!