although complex and complicated sound alike, they do not mean the same in this context.
The Zen therefore says: It is okay to build very complex applications, as long as the need for it is reasonable.
To give an example:
counter = 0
while counter < 5:
print counter
counter += 1
The code is very easy to understand. It is not complex. However, it is complicated. You do not need to manually perform most of the steps above.
for i in xrange(5):
print i
This code is more complex than the above example. But: knowing the documentation of ´xrange´ you can understand it by a single glance. Many steps are hidden behind an easy-to-use-interface.
As processes grow bigger, the gap between complicated and complex gets wider and wider.
A general rule of thumb is to follow the other principles of the Zen of Python:
If it is hard to explain, it is not a good idea.
If it’s easy to explain, it might be a good idea.