You have to remember to always keep both rear wheels turning.  Its harder now with the more powerful wheel motors.  On the Scag I learned on almost 20 years ago it was super easy, but you couldn't mow much of a slope with it.  Basically what I used to tell people that complained about that problem was that even though its a zero turn you can't lock the wheel down to turn or you'll gouge it.  People don't want to hear that.  Its cool to zip around on your shiny zero turn but it takes some care to make the yard look like it was mowed with a conventional tractor mower.  On most of my yard I don't care but it bugs me when I see "professionals" gouging up good turf when I used to take care to keep it from happening, even using the 445 Deere to make sure it looked good.  Pet peeve I guess.