Coobie I've owned a ZD21 for six years with the phase one hydrastatic pumps and my concern with the purchase of a new ZD is the fact that Kubota hasn't done a good job of protecting the hydraulic system from contamination and debris from clippings. Pay particular attention to the breather cap after cutting heavy dusty grass. More later after I do some personal testing on the new system. Good Luck with your new purchase.