I've completed my Z2-2 challenge run, although I missed out on the alternate ending route. I've finished uploading playthrough vids
of almost all scenarios. The full challenge conditions are included in the playlist description if you're interested in reading them. Anyway, it's the only fast paced gameplay walkthrough of Z2-2 on youtube, as opposed to the others that are all focused on animations and dialogue and such and take hours to watch a single scenario.
Like most SRWs I've played, the late game plays much differently from the early and mid game. The early and mid game is mostly concerned with dodging, defending, support attack/defend and countering, while the late game shifts to a focus on MAP attacks, support seishins like Enable, Hope, and Supply, and high damage attacks. I like the change of pace as you get to experience the game in a different way and aim for even lower turn counts than the first half of the game.
Route choices: D (Kummen), B (Space #2 Route), C (Space #3 Route), A (Dark Continent Route #2), B (Frontier Fleet Route), A (Normal Ending Route).
Final turn count: 261 turns / 60 scenarios (4.35 avg). There were a few scenarios I didn't feel like replaying for a lower count, so I know there's room for improvement here. Not a lot of room, though. Anything under 5 average is pretty good in my books, whether it's a challenge run or not.