I am currently stuck on that same battle, but I admit to doing a bit of googling to try and find a tactic which has worked for others as I was getting pretty frustrated, spending a good amount of time building my army and pushing forward only to eventually get wiped out, like 4 times. So the sequence I am going to be trying next is after destroying the 2 towers, continuing to use that on the rest of their army and hopefully destroying almost everything, then going in and using the solo which stops them from producing more troops. In my previous attempts I had always backed the tank thing out after destroying the towers rather than pushing forward with it. Hopefully it works this time, I actually am all set up to go in and destroy the towers, have had it paused for a few hours busy with other stuff.
****, failed again. Christ this part is hard, I am honestly sick of it because it takes so long to redo and it's like once they destroy most of my units at the front, even if i spawn more they start marching on my base rather than staying on the bridge and it's futile.