Consider this sentence -
My family and friends would say (that) X is the driving force of my life.
We don't know what X is. So
My family and friends would say what is the driving force of my life.
My family and friends would say is the superordinate clause or main clause. The subordinate clause is what is the driving force of my life
Here in subordinate clause is is the main verb. What (X) is the driving force of my life
Subject - What (X)
Verb - is
Predicate - the driving force of my life.
So we form the question this way -
What would my family and friends say is the driving force of my life?
My family and friend would say is the main clause. So notice how the verb would is coming at the front of the subject.
To learn more about this, please go through this answer. @F.E. has written a fantastic answer there.