Java Vs Zope,Python

I am a J2EE programmer and about to start learning zope and python. can anybody who knows both j2ee and Zope, tell me some comparative study of these technologies? i would like to know that can Zope and Python entirely replace J2EE? do they have that potential? people around have been saying lot of things about zope (mostly good)…if its really so good why people are not using it on large extent and for large projects….

A real professional and technical answer on this issue would be appreciated….