Mike H - Yes a Z1000 is more than enough.
Raising4Daughters - My layout is roughly 30x 50 with four loops on the main table and 4 powered districts (basically loops but connected to the main). I use one TIU for the main with each channel powering a loop ( although I could have powered all four with one transformer, I used 2-Z4000's). On the other table I use 4 Z-1000 Bricks to power that TIU. TIU's are set to operate together and I have had NO PROBLEMS.
You did the right thing by buying Barry's book and setting up like he suggest. Your problems will be minimal. I started back into the hobby in 2013 and purchased MTH. I now have Lionel and Atlas along with a Williams. As you grow Barry's book will answer 90% of any questions with the rest being answered here. JUST REMEMBER in your posted question include Make of train, Number (20-21264-1 as an example), How you are powering layout, and What items (TIU, AIU, Legacy 990, Z1000, etc). It will speed up an answer from here on the forum. This forum is always the go to place to ask. Best people with experience trying to help everyone, whether new of experienced.
Both of you enjoy the trains.
Arnold - you already know all this so continue having fun and keep asking questions. None of us know everything!