My playthrough of 59 and 60 (Gold for both) :
https:// youtu . be/xjjNhKwpdMk
TL;DW : The enemy massed on the right but didn't bother to push across (likely due to AI where if the route is blocked they stop trying to go there) so I slowly went from the left, took the airport and bomber-spammed.
https:// youtu . be/Nr5iRG81H-E
TL;DW : Built bombers and fighters while slowly pushing from all sides. I believe I got lucky because the enemy used their special on the other AIs instead of me.