What is the ruling on saying "yahūl" (it transforms/changes) or "lā ḥawl" (there is no power/might)?

The word "يَحُول" (yahul) varies depending on its diacritics (tashkil), conjugation, prepositions, and context.

It is permissible to say it if no corrupt meaning is intended.

As for the phrase "لا حول" (la hawla), it is idle talk and has no meaning outside of its context.