Currently kubectl doesn't easily show which GCP project and cluster you're working on. This solution adds relevant info to the Bash / Z-Shell prompt.
Based on: https://pracucci.com/display-the-current-kubelet-context-in-the-bash-prompt.html
Add to your .bashrc or .zshrc:
kube_prompt()
{
kubectl_current_context=$(kubectl config current-context)
kubectl_project=$(echo $kubectl_current_context | cut -d '_' -f 2)
kubectl_cluster=$(echo $kubectl_current_context | cut -d '_' -f 4)
kubectl_prompt="k8s:($kubectl_project|$kubectl_cluster)"
echo $kubectl_prompt
}PROMPT='[%D{%F %T}] ${ret_status}%{$fg_bold[green]%}%p%{$fg[cyan]%}%2d %{$fg_bold[green]%}$(kube_prompt) %{$fg_bold[blue]%}$(git_prompt_info)$(hg_prompt_info)%{$fg_bold[blue]%} % %{$reset_color%}'
Or just:
PROMPT="${PROMPT} $(kube_prompt) "PS1="($PS1) $(kube_prompt) "