Hi KayFe
Having kept pygmy cories for a short time, one of several conclusions I came to at the time was that there ought to be more of them than just 6. I also felt that, when in a tank with larger species (in my case harlequin rasboras and x-ray tetras, so roughly the same size as zebra danios), that micro-sized fish such as pygmy cories and ember tetras would do better in larger numbers - perhaps double the quantity. Translating that to your situation, I'd recommend 12 pygmy cories (if 6 panda cories) and double the number of ember tetras to zebra danios - but only if the Community Creator / Fish Profiles section of this website suggests that your tank dimensions and capacity would accommodate this safely. Since then, it also seems that the LFS (Maidenhead Aquatics) recommends that the micro-sized species are kept in groups of 10+.
Someone else will hopefully be better placed to comment on whether danios would be alright temperament-wise, etc, with your other fish.
It's also worth checking out whether your water is suitable for your proposed fish - look at your water/utility company's website, input your postcode, and find out what the various readings are for water hardness (eg in degrees Clark, French, German). These can then be translated through to whatever unit of measurement Seriously Fish uses for the particular species you're thinking about - it is similar to the Fish Profiles section on here but goes into a bit more detail on the specific requirements of particular fish.
Hope this is helpful.