User @Pablo answered this question that concludes that Naruto has killed white Zetsu clones. Due to Naruto's chakra, the Zetsu clones turn into trees. The reason is written in this Quora post and wiki:
Due to their genetic structure, direct contact with somebody that exudes a powerful life force, such as Naruto in Nine-Tails Chakra Mode, causes them to turn into trees.
Naruto didn't have a killing intent(?) but due to Naruto's chakra that exudes life-force, they converts into trees (which is a somewhat of a life-form). I have commented under his answer:
Naruto's chakra caused them to turn into tree. Would it be considered killing? See comments below the first answer*. I would consider it immobilisation rather than dead. Besides they are turning into trees which is not something dead (converting to one lifeform to another)
*Comments below first answer:
He killed multiple white zetsus though ;) – Sahan De Silva Mar 24 '17 at 9:33
@SahanDeSilva he made them into tree, so not really dead – Ankit Sharma Feb 17 '19 at 6:46
Question: Does Zetsu clones die when it gets converted into trees? Is it more of a immobilization rather than dying?