Zac Williams started playing rugby league for Monmouth Comprehensive in the Champion Schools competition. After being spotted by Lee Cullen, he signed for the South Wales under 15s academy eventually progressing to the 16s and 19s as well as the WRL AASE Academy having to move from Monmouth to Bridgend in order to attend training in Maesteg. He signed for South Wales Scorpions first team for 2015 and became one of only three players to have turned out for all ages levels and first team for the club. He has also played rugby union at junior level for Monmouth and the Dragons academies. A Wales under 16 and 18 international in Rugby League in addition to his Commonwealth Championships appearance in 2014. He made 54 appearances for the South Wales first team in League 1, scoring two tries, before joining Coventry Bears. He also spent some time on loan to French Elite 2 side Le Reole XIII.