Well long story short, it started when Zac appeared in battle bunny Riven her splash artAfterwards a lot of people (me included XD) started pairing them up because of their mixed personalities. I guess there is something cute about the bad ass warrior girl and the kind/goofy guy pairingsAlso they surprisingly hae a lot in common! Both have been harmed by the reckless use of Hextech from Zaun, both seek purpose and a place in this world, and both overcame what they were "originally meant to be" in order to help othersAs such the pairing grew really popular really fast ^^