Base model or sport model with SRM?
If you have SRM, use it to 'learn' how the car wants to be driven. Then turn it off and try to mimic those same shifts.
If you don't have SRM, try slowing down your shifts at lower RPM gear changes. If driving hard and fast, the Z likes quicker gear changes. Try different things and you'll quickly feel what she likes
For the record, 1st and 2nd gear shifts in the Z34 aren't like other MT cars. But you can make it smooth with some practice and patience.