Downtown Aquarium in Denver and in Houston are both AZA accredited. Fort Worth is accredited by both.
From what I know of ZAA, they are less concerned with overall rules that all facilities need to follow such as free contact (the main reason Pittsburgh left AZA). While any accreditation is good to have for a facility, not all accreditation bodies are built equally or look at the same things. For example, here are the accreditation requirements for both associations for conservation:
ZAA:
AZA:
While similar on the surface, especially with animal management, the AZA seems to be more concerned with specific aspects of a facility's conservation program. AZA is more of a micro-manager per say. This IMO is a good thing as specificity can force facilities to improve these aspects rather than put on a facade of "conservation" and require proof that things are actually being done.
Another probably better example of this are the requirements of both bodies for Education and Interpretation:
ZAA:
AZA:
Here you can see a real difference. ZAA requires only that education be a part of the mission statement, that they have a written plan regarding education goals, and that they have educational graphics. AZA requires that depending on the size and category of the facility, that they have a dedicated staff (or full department) dedicated to education, have some sort of contact with local academia, outreach, etc. Much more in depth and IMO in line with what an accredited facility should be striving to do. To me, the requirements for ZAA accreditation allow for a facility to get by without having dedicated education staff or programming as long as they have a "written plan" and education is a part of their mission plan. Not enough in my opinion.
Here are both bodies' accreditation standards for anyone who wants to compare and make their own opinions (
AZA) (
ZAA).