Zero-turn lawn mowers–also known as zero-turn-radius or “ZTR” mowers–have exploded in popularity, and it’s easy to see why.

John Deere has made plenty of big machinery in the past, but this one is the green-and-yellow’s largest ever. It’s called the 9RX 830, and thanks to its 18-liter turbodiesel engine, it’s also the most ...