I've had both models, multiple of each brand (fyi I don't own any swaro or Leupold rifle scopes anymore).
Z5 would be a closer comparison to the vx5hd in terms of magnification. The Z5 series uses "dual erector springs" over just one in the z3. According to Swarovski, that's supposed to make the Z5 series more durable than the z3. The experiences Ive had with Leupold have been bad, except for one. Every Leupy my dad or I have purchased since around 2010 to 2012 have failed. Either a RTZ failure, failure to track correctly, or complete failure of the erector assembly. All were CDS systems. We have one of the vx-3Ls with the cut out on the bottom of the objective from like 2005. That one's never had an issue but, it also doesn't get dialed.
I've had multiple z3s, z5s, and a couple z6s. Never had problems, but they didnt get shot much either. I sold them all.