B/X Known World
I mean…just make it up. That’s how you get new monsters. It doesn’t matter what the books says. Make your Yellow Musk Zombies different. Or just name them something else.All of those examples are monsters that you, I, and any other experienced DM have probably run dozens if not hundreds of times; and thus we've largely memorized what makes them tick.
If I've ever run a Yellow Musk Zombie, though, I don't remember it; and I'd have to check all three books to find its write-up and stats. Or a Fog Giant - there's Giants in all three books but after the basic Hill-Fire-Frost-Storm, which one's in which book? Or an Yrthak, which isn't in any of the 1e books but is in the original 3e MM.
If there's to be a new monster book, it's an opportunity to tighten up and consolidate the stats for all of them - as in, every monster D&D has ever had - in one place; specifically intended to make it easier for a DM to find and run any given creature during play. Leave the fluff and lore and fancy art for other books.