I might have found it. If you have annoying lag spikes while playing Zero Hour against a number of AI players, this is for you.
As Rise of the Reds mod version 1.7 for ZH became available, I played a match against a bunch of AI's, and I noticed the lag that has been bugging some people (I doubt me being the only one). So once again I searched the internet for solutions, and I found something that decreases the lag so there should not be lag spikes (game slightly slowing down at most). I don't remember the website, but it was some archived forum page. This may not work for everyone, but I hope it does as it did for me.
Here's what I did:
1. Create a shortcut for your GENERALS (not ZH), and add to the command line -forcebenchmark, for example:
Run the game, and exit after reaching the main menu. The game may not start at first, but wait a bit and it should start normally.
"C:\Games\Command & Conquer The First Decade\Command & Conquer(tm) Generals\generals.exe" -forcebenchmark
2. Go to the folder where your Generals is installed, and locate file Benchmark.txt. Open it, and you should see a line of text. Copy it.
3. Go to the folder where your Zero Hour is installed, and open file INIZH.big with FinalBig Editor, you can find it here: http://www.cncden.com/cncgen_utility_downloads.shtml
4. Once you've opened the INIZH.big with FinalBig Editor, look for GameLODPresets.ini, and extract it to your Zero Hour/Data/INI folder, for example:
C:\Games\Command & Conquer The First Decade\Command & Conquer(tm) Generals Zero Hour\Data\INI
5. Now open the GameLODPresets.ini with notepad, and you should see 4 lines of text with words "BenchProfile = XX XX XX" (X's are random numbers and letters). Now paste the text you copied from your Benchmark.txt after the 4 lines. Mine looks like this:
;Benchmark profiles for some common hardware configs.
;Only used to classify unknown hardware configs.
BenchProfile = P4 2189 6.108187 15.113676 9.402223
BenchProfile = P4 3049 8.640481 21.329025 12.888884
BenchProfile = K7 1500 6.978142 16.116205 9.252953
BenchProfile = K7 1009 4.679312 10.506442 6.062261
BenchProfile = XX 3003 15.609439 34.905502 21.071182
... continues with lots of text
The red line is my copied benchmark.
Using windowed 1024 x 768 resolution and Retarded Lag Patch, I could play match with 4 hard AI's and another match with 6 hard AI's, and I didn't get any lag spikes, just somewhat decreased game speed in some places with lots of action. But it wasn't "annoying" lag. I'll play in full screen mode soon to see if it still works.
Hopefully this helps people at least a little.
(BTW should this be in support section?)