ZFS = Z File System, a next-generation file system from oracle
ZIL = ZFS Intent Log
SSD = Solid State Drive, a type of long-term data storage system with better read/write speeds than an HDD
NAND = not actually an acronym, but a type of logic gate. Not AND.
Dictionary.com uses same definitions for both words, just in a different order. The first definition of acronym is when initials form a pronounced word; which is the second definition of initialism. So they're the same thing with the difference being vernacular.