New era.

What difficulty level did you play on? I'm just mildly confused by your story about clearing the map with Zehir. On Hero difficulty, all the starting packs are impossible to clear with Zehir, period. You can only take one stack at a time, like the 100 Goblins guarding the Goblin building, or the 50 Dancing Blades guarding the gold. All the other stacks are much stronger than these, and they're also upgraded. It's simply impossible to clear them with Zehir. And the same goes for Gothai, because his army won't be enough to clear even the basic weak neutrals in the center of the map before the inner garrisons. And the guards at the Orcish buildings are even stronger than those in the center. I had Gnomish Priests (30-40) guarding them, along with 100-120 Specters, 5-6 Cyclops, and others. So, I cleared everything with a female hero using archers, and as a result, I didn't accumulate enough of an army by the time the first hero arrived to counter it. I still don't fully understand what I need to do to accumulate enough troops. The neutral stacks are very tough; the previous Master campaign was much easier than this mission. Gothai is generally the easiest to play (Orcs aren't a problem, and he always crushes everyone), but you need to capture his buildings first. In general, I cleared the entire center before the inner garrisons, but I didn't have time to reach the mines. I also killed everyone around the perimeter of Zehir's territory, except for those above, where the Orcish buildings are, and inside the perimeter. I cleared half of the forest to the right of the center, and half to the right above the forest, up to the building that upgrades unit classes. This took me a month and a week, and by that time, the central Demon castle appeared, and he easily killed me. None of the reinforcements arrived; I didn't even understand what I needed to do for them to arrive. It says that you need to capture the outer garrisons, but how do you capture them in the first month? There's no way. As a result, they died without even appearing on the map.
Overall, I came up with a few ideas on how to improve the start, but even if I gather all the troops of one hero and clear Zehir's territory (I'm not even thinking about Orcs, you need 6-7 units in the army to clear them), I still don't see a clear advantage over the first Demon. I'll probably try on Veteran difficulty, with an Unaligned hero. I suspect that the campaign might be conflicting with Eve, which enhances the AI and units on the map. I don't remember all the buffs of this mod anymore; I downloaded it a long time ago. I remember looking for ways to make the bots move faster and the neutrals stronger. Maybe that's why the neutrals are so tough in this campaign. Although I downloaded other ones recently and successfully completed them; I didn't notice anything like that, I would even say that everything was very easy.
And by the way, Zehir's ability doesn't work for me. Elementals don't appear after a unit dies. So something is wrong.
I've completed all the previous maps and Master campaigns, and others, with this mod, so I still think the problem isn't with it. There are no other campaigns in the folders, there are only 3 multiplayer maps, two of which are Master campaigns and one is Ganrithor, where there are no mods or special scripts.