The ZS’s voltage input range is from 9V to 15V which means it will re-regulate it internally. The result could be better, or worse (if you spend $$$$ on a power supply by cost-vs-effectiveness perspective). So I personally think just go with the power supply unit shipped with original package, or no more than iPower 2.
This has made my system sound significantly better - cleaner, more open and dynamic, and video is better to. Mine powers the Zen, a TiVo, my router and a Fire stick. I tried the Zen on the 12v tap but prefer the sound at 15v
If you have multiple DC powered devices, the HD Plex is worth a close look. Note that the fixed outputs can be customized for your needs. Mine has two 12v taps