I recently came across information in an article where a Mufti equates the Khilafah ruling to Zakaah.

Answer

We do not know what the Mufti means by equating Khilaafat to Zakaat. In fact, it is of a lower status than Zakaat. Zakaat is Fardh. Denial of Zakaat renders one a Murtad. Khilaafat despite its extreme importance is Waajib, not Fardh as is Zakaat. We do not understand the understatement of 'just a part of Islam'. Every part of Islam is of extreme importance.

It is stupid and disgusting to say that Khilaafat is 'not of importance'. Since he has equated Khilaafat to Zakaat, it follows on the basis of his logic that Zakaat too is not of importance. Such a belief is kufr.