'exec fish' at the very bottom of my '.zshrc' - is it possible to bypass it?

I prefer to use the fish shell on macOS most of the time, but refrain to make it the login shell, because I think sometimes it may cause problems. So, I simply added exec fish at the very bottom of my .zshrc, and that's it. Which means my login shell is still zsh, and my $PATH modifications are still in .zprofile, but when I open the terminal, I don't have to switch to fish manually. Works fine for me. But then, what if I nevertheless want to switch from fish to zsh for some specific reason? Is it possible somehow? (Because if I simply type zsh and press Return, I will be immediately switched back to fish, of course.) **update:** There is a workaround to use zsh -c, but it works with some commands only.