I think you want parameter 16 for physical dimming speed, but you have been only setting parameter 9 for ramp rate control.
https://thesmartesthouse.happyfox.com/kb/article/538-zen72-dimmer-switch-700-advanced-settings/
You may need to use the Basic Zwave Tool to see what these are set to, and to change their settings if they aren't exposed in drivers. But my Zen77 are in the community driver at least, so I am not sure why you wouldn't see it for the Zen 72 also?
