What is the difference between complacated and complicating?
Drivers must know their directions backwards and forwards, which is a complicated/complicating task in the maze of London’s one-way streets and blocked-off pedestrian zones.

Could you explain to me so that I could understand once and forever.

Question

What is the difference between complacated and complicating?
Drivers must know their directions backwards and forwards, which is a complicated/complicating task in the maze of London’s one-way streets and blocked-off pedestrian zones.

Could you explain to me so that I could understand once and forever.

Answer

Complicated refers to something that is difficult to understand or very intricate.

Complicating means to make something more difficult or confusing.

Answer

Complicated is a participle adjective.  It looks like a past participle verb but it's an adjective.  It describes a situation or event.
Complicating is a verb. It does not belong in your example sentence.  
Use it in continuous tenses like this:  London's streets are complicating the problem.