I challenge you!

It seems that on this map, the computer receives an army through a script.

Yes, through a script, because the computer cannot visit obelisks that increase the level, or treasure vaults with artifacts. Also, if you don't give it an extra army, it becomes passive towards outposts or cannot break through them (you have to increase their priority through a script). It only buys artifacts from shops, and since the script provides a lot of money, it will buy a Phoenix even if it gets the chance.
If it's a difficult "Warrior" difficulty, you can also play on Recruit difficulty.

For example, on Hero difficulty, and even on Veteran, the enemy hero runs up, kills the main hero, or rather, I manage to escape. Then, it captures mines and starts clearing the map and capturing the central Castle, but the city is safe until it captures an outpost and a Castle. We buy back the fleeing hero, wait for the beginning of the next week, buy an army, use a "Cockroach" to retake the mines, the main hero runs through a portal in the underground to the corner Castles and cleans up what's left, preferably managing to buy a Phoenix (that's why we don't take experience from chests, but take money, and capture gold mines in the vicinity). If a level 2 regeneration guild member arrives, then half the battle is won, and it's even better with light magic. We put him on a Phoenix and clear out the remaining strong neutrals, as the computer is afraid to attack them. On Hero difficulty, unlike Warrior, it is very desirable to visit an obelisk that increases the level to 15. For improving low-level units, we use a Fort, as it is simply cheaper and you don't have to build buildings in the Castle (but only up to level 3-4 units). The main thing here is to get as much gold and other resources as possible, and for this, you need "Cockroaches" (we find them in Dungeons, so as not to spend gold). If we have the Warlock faction, it can withstand two attacks from enemy heroes, but the army becomes significantly depleted, so you need to quickly switch to thick Hydras, or use Invisibility properly with a good mana reserve.

This is one of at least three tactics against the computer that I have tested on Hero difficulty. Many things change in this tactic against a "Squirrel" opponent.