Why do you need to source .zshrc for every new shell in iTerm?

Make sure your export/source are added after the plugins in your zshrc, as stated in this post: oh-my-zsh config file not loading

I had the same issue and changing the Shells Open with option fixed this for me.

To get here:

• Open Preferences for Terminal
• Select the General Tab
• Change Sells open with from Default login shell to Command (complete path) with the /bin/zsh in the input box.

Screeshot:

On starting a new shell just run the command source ~/.zshrc by configuring in the

Preferences -> Profiles -> Select Default Profile(default profile will be starred) -> General -> Command -> Select Login Shell -> Send text at start:

Enter the value source ~/.zshrc.

You may add source ~/.zshrc; clear in case you need to clear the screen contents after executing the command.