# ^Xa to insert all matches
zle -C all-matches complete-word _generic
bindkey '^Xa' all-matches
zstyle ':completion:all-matches:*' old-matches only
zstyle ':completion:all-matches::::' completer _all_matches

UPDATE: The snippet above brings insert-completions to zsh. Thanks, Trevor Joynson, who has provided the solution in comment.

Command insert-completions (see man bash) is the feature I most miss in bash.

[insert-completions] Insert all completions of the text before point that would have been generated by possible-completions.

Its default binding is M-*, a.k.a, Alt-Shift-8 or Meta-Shift-8.

It is useful for simple batch operations, such as removing all git branches starting with feature/.

After I switched to zsh, I have been looking for a similar command, but for no results. However, I just discovered the zsh way to select multiple completions recently, using accept-and-hold (see man zshzle).

[accept-and-hold] Push the contents of the buffer on the buffer stack and execute it.

The default binding is M-a (a.k.a, Alt-a or Meta-a). If the command line has input content ls, M-a executes the line ls without clearing the input.

It seems unrelated. But if completion menu is activated and a menu item is selected (the simplest way is Tab twice), accept-and-hold accepts the current menu item without closing completing menu. So it is possible to select multiple items by navigating to wanted items, and type M-a to select them.