The Toyota Way is a philosophy that includes Kaizen, Lean, and like 12 other principles. http://icos.groups.si.umich.edu/Liker04.pdf. Most people latch on to one or two because the whole thing is too big to grasp at one sitting. It takes a long time (a century, for Toyota) to develop a company into it.

I'd say that kaizen is a lean technique for improving a process or flow as described in "Lean thinking".