Digitization is more concerned with the platform and mode while digitalization focuses on the process and way of doing things.
When data is computerized and available in a computing device like laptop, computer, or mobile phone and is no longer utilizing a pen-and-paper mode, this can be called digitized. On the other hand, when data is digitized plus it can also be useful, processed, and meaningful and it is in synchrony with the process and operations of an institution or activity, this refers to digitalization.
In other words, all digitalization includes digitization but not all digitization qualifies as digitalization. This is because digitalization requires a step higher than mere putting of data to a digital tool; it is characterized by a cultural and organizational integration which means human processes are in harmony with digital processes to accomplish a goal.