Arrow and Izombie are in the same universe
Here is why the bad guy on Izombie Blaine deBeers The one who turn liv moore into a zombie is on the arrow universe because the actor who plays Blaine deBeers played a minor role in arrow and he has the name Cyrus Vanch which I believe was an alias used by Blaine deBeers before he became a zombie on I zombie since the actor plays a crook on both shows this could be a possibility just look it up on the arrow wiki and the I zombie wiki since they both are a DC studio shows it could be a possibility that they share a universe http://www.ksitetv.com/forums/showthread.php?173431-Arrow-and-Izombie-are-in-the-same-universe