I haven't been able to log into dream zoo on my ipad for over 6 months. I have contacted Zygna and they have said they are aware of the problem, but with every update since then it has not been fixed. Zygna are a terrible company, they just keep updating with new items to purchase and never seem to fix the bugs. I play Dream Zoo now on my Galaxy and it pretty good, it crashes sometimes but is far more stable than on the ipad.
I also can not log into Cityville Hometown it crashes all the time to. There are some good games out there now very similiar to Zynga games and a lot more stable.