Zenoss 4.2.5 - install extra libraries for use in a zenpack

from cryptography.fernet import Fernet
f = Fernet(encryptionKey)
unencryptedvalue = f.decrypt(encryptedvalue)

but i'm struggling to get it to work once i add it as part of my zenpack code.
I get errors that the module cryptography.fernet cannot be import - i.e. it can't see my packages.

I'm not sure if the issue is when i installed as root the libraries end up in the out of the box python26 area but zenoss is actually using the /opt/zenoss/lib/python and python2.7 area to pick up its packages.

I did do some experimenting with various attempts to install the packages (cryptography pulls in some dependencies - six, idna, pyasn1, enum34, ipaddress, pycparser, cffi) in the python27 area as the zenoss user via either manually running the setup.py files for each packages or running a pip explicitly using the /opt/zenoss/bin/python like this:
/opt/zenoss/bin/python -m pip install cryptography

but doing this seems to get me in a mess each time with zenoss itself starting to throw problems up when i restart the daemons. (Fixed by reverting to my pre install attempt snapshot of the VM)

So i'm not quite sure how i'm supposed to install the libraries so that they work with the zenpack and not break zenoss in the process!
The six library seems to cause issues as there now seem to be vaiours versions of it spread across various directories...

Could i solve this by adding the libraries directly to my zenpack so that only that zenpack code uses them? (similar to the advice in this thread - How to add required Python module to ZenPack)

Any advice appreciated

Thanks
Dafydd