I am not familiar with this mower (ZG1272-54), what brand is it? I have an older JD 757 (7 Iron) that has about 600 hours on it and it has performed flawless since 2005 under pretty tough use with regular maintenance. The new JD's have had some issues, particularly when they began manufacturing them in China. The preferred ZT by the professional lawn services here are Exmarks. However, they are pricey and used ones in decent condition are hard to find. Check out one of the lawn mower forums and see what they have to say about them. If you are buying from a private owner your are more or less on your own unless you get some sort of written warranty and even that could be very expensive to enforce. A good, reputable dealer in your area may be your best bet and he may be willing to give you some kind of conditional/limited warranty and possibly try before you buy.
Good Luck on your quest.