Accessing under the deck of a zero turn mower is both a crucial and inevitable part of owning such a machine. Some high-end commercial front cut mowers feature an electric lift to flip the deck up, negating the need for a lift. It is not as simple as flipping a switch for the many owners of mid-mount ZTR mowers out there, but there are options available.
Safety is paramount when attempting to lift any heavy machinery, it is always better to spend a little and be safe than skimp and be very sorry.
Solid rubber ramps are a low tech, relatively inexpensive, yet very effective option. Blitz, who also make ramps for cars, make the EZ Lift Rider Ramps for mowers which can usually be found for less than $30 online. Wheel chocks make a great addition to such a setup. An added benefit of ramps is that they are relatively small and light compared to other options, so won't take up a lot of room in, for example, a trailer. A common problem with ramps is that they will slide when on smooth surfaces (driveways for example) and can leave unsightly marks. They also do not give you as much clearance as other options.
Floor hoists (often called cherry pickers) are an option but are expensive if not already owned.
Forklifts can be used, but obviously they are not exactly common in the average residential garage.
Luckily there are companies out there producing specialized lifts to suit zero turn lawn mowers. MoJack is an example of such a company. MoJack offers a range of lifts to suit all needs, from the garden variety "big box store" lawn tractor, to the heaviest commercial ZTRs. The Mojack MJEZ is one of MoJack's most popular products. It has a 300 pound capacity lift (the lifting capacity refers only to lifting the front of the mower, not its total weight) so is suitable for homeowners and light commercial use. Heavy commercial users might look to the MJPRO from MoJack which has a capacity of 750 lbs. MoJack offer a warranty too for some extra peace of mind - two years for the residential user and one year for commercial users.
The T-5350 from Pro Lift is another popular mower riding mower/lawn tractor lift which has earned rave reviews from all corners of the mowing community. The T-5350 uses a hydraulic pump for lifting. Other brands use a screw lift. Like most hydraulic lifts, the T-5350 from Pro Lift has a mechanical 'safety' mechanism which would engage in the event that the hydraulic unit began to leak.
A lift is a great idea for commercial landscapers. In such a competitive field, every little edge can help. A lift allows mowers to be maintained quickly and efficiently. Common maintenance tasks such as deck cleaning and sharpening blades, for example, become much less time-consuming and laborious tasks when a ZTR lift is employed. A lift may also potentially save many expensive trips to a repair shop. When a fleet of ZTR mowers is involved, as is often the case in a commercial setting, the time and economic savings from a lift are magnified.
Storage space can potentially be an issue with lifts as they are often quite bulky even when disassembled, although most will pack away flat. Given their usefulness the space they take up is not unreasonable.