Wizard – “Liberation” [Campaign 6, Mission 2]

I'm so fed up with this mission... from the portal, starting on the second Monday of the week, two creatures keep appearing, and there are already about 100 archers, 30 ghosts, and 25 vampires, 70 zombies, 10 liches, and a bunch of undead, about 5-7 each... they defeat me easily... I can't move away from the city. Moreover, both heroes are very skilled in Resurrection and actively use it... I've already tried about 15 times...
What should I do?