I almost always use zsh, but occasionally have a reason to switch back to bash. It's so infrequent that I can't even think of a good example.. but I put all of my aliases and functions in ~/.profile and make sure that my bashrc and zshrc explicitly source so I have them all in either shell.
I maintain inshellisense & I've been contributing some features to VSCode's terminal which both require in switching a lot between shells for testing. I kept trying to run my git specific aliases in other shells and decided to make this to unify them