I just freshly installed El Capitan on my MacBook Pro. I had trouble earlier with the my terminal being too slow while typing in simple commands. I thought it might have been that I need to format my drive and install 10.11.

After re-installation. It turns out nothing changed. Still my iterm is very heavy. When I tried to further investigate this, it turns out that I don't have this problem when running on a bash shell. I only have this issue with Zsh.

I use homebrew, iterm2, and oh-my-zsh. I hope someone can shed some light on this. Thanks.