Struggling in the middle game with Zeus v Norse

I just played a game on Midgard vs a Thor player. I won the water early on and killed most of my opponents fishing ships. Behind that I went for a 2nd TC and started building toxotes. But my opponent went quickly up to Mythic, attacked me with fire giants and throwing axemen, and just as I was beginning to clear them out 100 heroes of ragnarok showed up in my main TC so I resigined.

A lot of my games follow this pattern where I get an early advantage but don't know how to push it. Then my opponent stabilises, goes Ragnarok and I lose. How should I be playing against Norse as Zeus?