emulate -L zsh
setopt extendedglob

local curcontext=:zle:delete-whole-word
local -a matched_words
# Start and end of range of characters to remove.
integer pos1 pos2

match-words-by-style

if [[ -n "${matched_words[3]}" ]]; then
    # There's whitespace before the cursor, so the word we are deleting
    # starts at the cursor position.
    pos1=$CURSOR
else
    # No whitespace before us, so delete any wordcharacters there.
    pos1="${#matched_words[1]}"
fi

if [[ -n "${matched_words[4]}" ]]; then
    # There's whitespace at the cursor position, so only delete
    # up to the cursor position.
    pos2=$CURSOR
else
    # No whitespace at the cursor position, so delete the
    # current character and any following wordcharacters.
    (( pos2 = CURSOR + ${#matched_words[5]} + 1 ))
fi

# Move the cursor and delete the block in one go for the
# purpose of yanking.
(( CURSOR = pos1 ))
BUFFER="${BUFFER[1,pos1]}${BUFFER[pos2,-1]}"