Nim Deathmantle's color-changing and type-changing effects override the equipped creature's previous colors and creature types. After Nim Deathmantle becomes equipped to a creature, that creature will be a black Zombie, not any other colors or creature types.
Nim Deathmantle
Once Nim Deathmantle returns a card from your graveyard to the battlefield, it will remain on the battlefield indefinitely, even if Nim Deathmantle becomes unattached from it.
Once Nim Deathmantle becomes unattached from a creature, its color-changing and type-changing effects stop affecting that creature. The creature will no longer be black and will no longer be a Zombie (unless its printed characteristics or some other effects still cause it to be black and/or a Zombie, of course). This is true even if Nim Deathmantle returned that creature to the battlefield from the graveyard.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Karl Kopinski
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
