I suggest that you read LlamaGuy's walkthrough first(http://www.neoseeker.com/resourcelink.html?rlid=51737&rid=48100)
as this tip only tells you how to destroy the town centre quickly.
As LlamaGuy said it in his walkthrough, this level might hold you up as they have seemingly endless supply of archers, knights, prophets and ballistae which I found really hard for my army to pass through. However, as I was playing the level for about 3 times, I found a VERY easy way to destroy the town centre (without using the Black Prince in battle!) provided that you have loads of resources (probably around 3000 to 4000 especially wood, gold and iron). This is how I did it:
After you have the resources, use some of your citizens to build a barrack and two siege factories between your base and the enemies base. Obviously, guard the citizens using the Black Prince and his army. Afterwards, create around 12-15 HEAVY RAMS (use both siege factory to produce the rams quickly) and then create around 10-15 PIKEMEN/LONG SWORDS. (You can produce more heavy rams/pikemen/long swords if you want.) Upgrade the heavy rams and pikemen/long swords to maximum especially the attacks and hitpoints. When all the heavy rams and pikemen/longswords are ready, select all of them and set them to attack the town centre. Just wait for the heavy rams to do their job and see the town centre crumble! Done.
Whilst I was playing the level for the last time (basically I was on the verge of quitting and I didn't want to load the saved game anymore) I build a huge army composing of cataphracts, simple bowmans, trebuchet, you name it! Then I select all of them to attack the town centre. Within seconds, my huge army died and I found out that the Black Prince was converted by one of the prophets! I was amazed that the game still continued. Since I have loads of resources, I experimented and created the heavy rams and stuff. I just thought it would be a great idea to share it.
This is the very first tip I ever made so if you have a shoutout, comment or anything you can e-mail me: firstname.lastname@example.org
Unfortunately, if you have any other questions regarding the game, I might not give you sensible answers since I am still playing the game. However, if I find interesting facts or anything, I'll keep you guys and girls posted.