How to add a zle-line-init hook without replacing existing hook?

I would like to run some code when zle becomes active. The only way I know how to do that is

zle-line-init() {
    echo hi
}

zle -N zle-line-init

But AFAIK this will replace any potential existing zle-line-init hooks. How can I either add to existing hooks (like how precmd has a precmd_functions array), or restore the previous state of zle-line-init after my function runs?