It really does sound like a fuel delivery issue - either the pump isn't keeping up with demand or a bit of crap floating somewhere in the fuel system that every so often is restricting flow but then floats free when the suction stops. I've had similar faults with carby motors but they usually stall all together. I would be seeing if your tech is open to a sea trial with a fuel pressure gauge fitted for starters or have a crack yourself. Not sure if there is a sensor for the NMEA output that monitors this in the Zuk's. Moonlighter????