I've been using my autoupdate in recovery to flash update.zip from a USB flash drive.
It works just fine and I've even flashed my poor Poke5 to Chinese and back again.
I can be so brave because I have a full raw backup, which I have EDL'ed in a few times.
But incremental updates can be problematical.
They need a lot of elbow room to rearrange the super partition.
Probably more space than you have RAM unless you have something with 4 GB or more.
Well, I'm working on this:
Code:
01/01/1980 00:00 670,998,528 product_a-cow-img.img.0000
01/01/1980 00:00 1,318,719,488 system_a-cow-img.img.0000
01/01/1980 00:00 298,991,616 system_ext_a-cow-img.img.0000
01/01/1980 00:00 451,747,840 vendor_a-cow-img.img.0000
As you can see, you need about 2.75 GB elbow room.
I could probably get this to work if I formatted a flash drive with ext2.