Whatever you do, when you compress the ZIP file, set it to STORE ONLY. Do NOT allow it to compress at all, else it won't work.
Make your bootanimation.zip have the following Tree:
- bootanimation.zp
\-desc.txt
\-part0
\\-<filename1 in numbered sequential order>.png
\\-<filename2 in numbered sequential order>.png
\\-etc.
In your desc.txt, make it the following:
480 854 2<enter>
p 0 0 part0<enter>
Save that and name it.
Then, make your PNG file(s) 480x854 px in size, make them look how you will, and save them as something like 001.png, 002.png, etc. Put them in a folder called part0.
Then make a zip file (I use WinRAR), set it to ZIP, with compression of STORE ONLY - this is SUPER IMPORTANT. Trust me, you want it to not be compressed, else it won't work.
Then, put it on your phone in the /system/media folder, set permissions to all checked, and give your phone a reboot.
If you have any questions, feel free to give me a shout. I have been doing a bunch of animations for a while (as my Custom BIOS-style Boot Animation link in my sig says).
Cheers,