We worked on them at the Kubota dealership. The bigger ones seemed to be good, while the smaller ones were garbage. Biggest problem on all of them was fuel transfer pump--it supplies diesel to the injection pump and incoporated a hand operated priming pump that you couldn't find or get parts for. Primer check valves crap out and allowed the transfer pump to suck air. Finally discovered someone had an adapter plate aftermarket and you could bolt up a Massey or JD priming pump right on it with a little bit of plumbing work. We sold every one of those adapters and pumps we could get in real quick. Common problem.
Water pumps were an issue as well. Impellors would get loose on the shaft.
Like a lot of Russian and East European stuff, Zetor thought massive steel meant better. That front end loader and the way it mounted was a royal pain in the butt and was in the way of any engine work you had to do at all. Lots of them around here but repairs could get into your wallet in a hurry.