Hi!
Thanks for asking first. 🙂
If you purchase the pack and use it for a single project, you're welcome to remake the assets in voxel form and adapt them to fit your characters and game style.
Please keep in mind that the license is for one project only, and the original files may not be redistributed or included in another asset pack.
Since the voxel versions would be based on my artwork, I'd appreciate being credited as:
"Based on graphics by Penzilla Design"
Good luck with your game development, and feel free to send me a link when you have something to show!