Depends on what you consider properly.
The TA-ZH1ES does have 10-times the power of the WM1Z and the HD660S or HD800S/HD820 still sounds bad with it.
The DMP-Z1 does have significantly less power than the TA-ZH1ES and people seem to prefer the sound of the DMP-Z1 with the HD800S above the TA-ZH1ES. But those have been all tested by different people.
I could drive the 300Ω Sennheiser HD820 without issues with the WM1Z, so i'd be surprised with the 150Ω HD660S would be worse
You should end up with 25-30mW with the HD660S, thats enough to drive them properly.
According to Sennheisers official Datasheet:
https://assets.sennheiser.com/global-downloads/file/9756/HD660S_Manual_042021.pdf the WM1Z should have enough power to make you deaf with them.
But to my experience, it won't sound good. The HD820 also didn't sound good at the TA-ZH1ES but did sound pretty amazing with the M11 Plus (which does have less than the half power of the TA-ZH1ES).
I think too many people mix up sound signature with power and see a correlation that is actually not there. Sennheiser Headphones don't pair well with Sonys Sound Signature imho, no matter how much power. I also disliked the HD820 on the DMP-Z1.
There is no other way than testing it for yourself.