This is just a dream in the farflung future and will probably never happen. I follow Snowleopard's threads and I got this idea from his. States- OH, IL, IN, IA, NE, WY, UT, NV, CA, AZ, NM, TX, LA, MS, AL, GA, SC, NC, VA, WV, PA, ON (Canada), MI, OH They would all be new zoos for me except- Cleveland, Toledo, Detroit, Erie, Pittsburgh, San Diego, Santa Ana, OC, Brookfield, Lincoln Park, Shedd Aquarium. And Brookfield took reciprocity.
Coast to coast is very far flung. It would make more sense I think to do one big trip in the eastern half of the country and a separate big trip in the western half. Plus if it will be a once in a lifetime trip I would think you would want to save time for other must see sights, such as Yosemite, Sequoia, Grand Canyon, etc.
South Central I was going to do a list, but I sent before I attached! I revised my far-flung plans for a zoo trip in New Mexico, Texas, Oklahoma, Arkansas, and Louisiana as well as Missouri and Ohio zoos. Arizona Docent, I understand that coast-to-coast trips are expensive and far-flung, but have you read SL's threads about his trips? They actually happen!