Finally! I successfully installed Yosemite (10.10.3), using the UniBeast/MultiBeast/Chimera installation procedures, and didn't have to use maxmem=8192. (Zorro has 16GB of memory.) If I didn't use maxmem flag, I'd get the dreaded "deadbeef" error. I couldn't figure it out...then, I remembered that Son-of-Zorro used a graphics card, although it only has 8GB of memory...
...so, I tried a spare graphics card (HD6450).
BINGO!! Runs as good as Yosemite should run, and iMessage works with FileNVRAM 1.1.4. (See
http://www.tonymacx86.com/general-help/110471-how-fix-imessage.html guide's
Chapter 6 for how to get and install FileNVRAM 1.1.4.)
HD3000 in Yosemite is the bad boy here. It's the infamous Yosemite framebuffer problem. Ugh!
For those of you who will want to stay with HD3000 and are having problems (deadbeef and other KPs), take a look at toleda's
http://www.tonymacx86.com/graphics/125239-hd4600-hd4000-hd3000-framebuffer-edits.html guide.
So, since Zorro is being used as a "production" system, I'll just keep the Gigabyte HD6450 installed and not waste anymore time on HD3000. My production system will still be Mavericks, but I'll keep "playing" with Yosemite to see it mature...maybe.