What kind of restrictions were you given when you wrote the book?
For Z&B, my main restriction was a CS bible that had been put together by some of the creators of CS along with a couple Microsoft guys. All of my zeppelins, bombers, and other mentions had to fall within the boundaries of their primer. I was able to decide most of the rules and designs, but it had to stay balanced, and the look of each nation's airships had to be consistent with what had come before. For example, the Black Swan's airship Huntress is a captured Texas airship, mentioned in Pride and expanded upon in Z&B.
I was given more freedom that I was expecting for both Pride and Z&B. I think the Air Rangers were originally envisioned as a law enforcement unit, but I saw them more as the air force itself. The rules are mostly balanced, and you can take two players who want to play a campaign against one another, choose starting income (let's say $20,000) and each go in completely different directions to build up their fighting force. Want to pay for better aircraft? You might have to skimp on veteran pilots. What about better rockets? You'll pay by having less fuel you can afford. Etc etc.
Were you given a certain timeline you had to incorporate and then free reign to fill in the holes?
I assume you mean 193X - 193Y. Not really. It was clear the game was going to progress the same as Battletech and Shadowrun did - slowly moving forward through events in the universe as new source books emerged. But the game universe was still so fresh that it it would have been awhile before we saw the light of day in 1938.

Did they direct you on certain character creation?
Not really, though Z&B isn't character heavy. For Pride I wanted Texas to have it's own heroes of the sky. Hollywood had them. The ISA had them. The pirates had them. Texas didn't really have one that appealed to me, which is where Phillip O'Malley came from. I wanted a rising star that had all the makings of a living recruitment poster for RTAF service. An ace pilot with a chiseled look and a sexy aircraft.
By the way, the reason the Mockingbird's tail seems to sweep forward is because it was my nod to Mooney Aircraft, an airplane manufacturer based out of Houston that is famous for it's "backwards" tail design. (They used to hold the world air speed record for turbo prop production aircraft.)
Were you surprised with what you were able to get away with if you tried to push the boundaries at all?
Yes! This was the best thing about working for FASA. Once they knew I had a complete vision for how Texas was supposed to fit into the rest of CS (and the rest of what they had established Texas to be), they cut me lose and said they could pull it back in editing if need be. I was able to exagerrate everything. Make the airships, the aircraft inventory numbers, the nation's GDP, everything bigger. I wrote Pride in the voice of a journalist turned propaganda writer, who willingly trades in a press hat for a government badge and puts a pro-Texas spin on everything.
With Z&B the same thing was true. For example, the heavy bomber for Hollywood is a 6 engined flying wing with three Bloodhawks mounted on top of it's dorsal surface. They can't reattach during flight, so they serve as passive escorts and deploy as needed, then after the threat has passed must find a place to land if they don't have the range to get where the bomber is going. They approved the concept and nearly every other one I put forth.
More to come...
Patrick