I'm using Zenfone6Z on last 6months. And i have tried to change Font style, but every time i failed. Because only 2 default font style is available in the phone (screenshot attached). When I was using Zenfone5, i have not faced like these issue and Zenfone5 have lot of default font styles.
So I'm requesting please include more font style in next update. Note: Without installing additional app have to change more font style.