zulip/docs/development/setup/vagrant-rebuild.md

If you ever want to recreate your development environment again from scratch (e.g. to test a change you've made to the provisioning process, or because you think something is broken), you can do so using vagrant destroy and then vagrant up. This will usually be much faster than the original vagrant up since the base image is already cached on your machine (it takes about 5 minutes to run with a fast Internet connection).

Any additional programs (e.g. Zsh, emacs, etc.) or configuration that you may have installed in the development environment will be lost when you recreate it. To address this, you can create a script called tools/custom_provision in your Zulip Git checkout; and place any extra setup commands there. Vagrant will run tools/custom_provision every time you run vagrant provision (or create a Vagrant guest via vagrant up).