Mckenzie began his songwriting work around 2010 with a full range of UK pop stars, achieving top ten hits with Conor Maynard and his number Number 1 UK debut album Contrast as well as the track Next Thing on Katy B’s Number 1UK album Little Red.
Then in 2014, Mckenzie teamed up with Australian rapper Iggy Azalea. He wrote 6 songs for her second album The New Classic. One track Fancy, featuring Charli XCX became a huge global hit. The song was Number 1 in four countries, went platinum in eight countries and became one of the best selling songs of the year. It was Number One on the US Hot Rap Songs end of year chart. The album was nominated for Best Rap Album at the Grammys in 2015.