Complex sentence: Nefertiti disappears from view somewhat earlier (around regnal year 14), the reasons for this are at present still unclear and under debate (see below), and around the same time a new co-regent is first attested.
Split into simpler sentences: Nefertiti disappears from view somewhat earlier (around regnal year 14); the reasons for this are at present still unclear and under debate (see below). Around the same time a new co-regent is first attested.