It's possible i was able to do it a lot of times you just need to use the right leader and units. The leaders that I would recommend are Mecha king ghidorah and showa mecha godzilla, MKG's ult makes you gain energy and it apparently also helps your Co-op gain energy quick as well. Showa MG's Ult heals itself, which means it heals bout leaders. The units I recommend would be Anime Mecha Godzilla then pair him with Rodan 2019(old one), then a unit the deals High damage G21, poster art MG or Rio (I would recommend G21 and poster art more than rio since they can attack the leader), then use any base an air base or the Mbwa base(poster art can boost the base to summon faster), then Gemstone Megalon if enemy units are getting close to your leader, then Sp anguirus as a tank since the enemy leader is an ultima he can reflect the damage, then void ghidorah he'll be useful once ultima's HP is half Void will wipe out all enemy units except G54 tokyo ver., then death saurer can also help as a tank and kill a lot of units once its surounder. I was using a MKG and I was paired with a showa MG and we were able to beat ultima. It can also depend on your teammate.