Starcraft – Do custom games of a higher difficult count for those below it for the custom games vs AI achievement

From the multiplayer menu, choose "Custom Games", Create Game, and in the game lobby, "Add AI".

"Evenly matched" in this case means you and the opponent AI have the same handicap percentage specified.

I've beat Terran with Protoss using photon rush.

1. Build probes constantly, 1st build probe will go to opponent, all others - go to minerals; 10-12 actually should be enough.
2. Build the 1st pylon outside of the opponent's start location - if you build it in the opponent base (after the choke) he will attack the pylon with large amount of SCVs. The Pylon should be built as close to the opponent base as possible.
3. Build 1 forge.
4. Build 2 cannons close to the opponent base - they will shoot up the ramp soon.
5. When these cannons are almost complete, send a probe to the opponent's base and build 1 cannon (you 1st pylon should give enough space for 1-2 cannons).
6. Opponent will try to attack your building cannon, but your first 2 cannons should be able to protect them. Keep you probe from being killed by SCVs/marines.
7. Build new pylon close to new cannon, once the new pylon is done, build 1-2 additional cannons not to far away from the 3rd cannon; it should be able to protect the new building. The new cannons should also be able to attack the command center.

After the last cannons been build they will start shooting the command center. The AI will give up quickly.

I did the above and finished sometime around 4:30.