Conditions that are fully contained within other conditions are referred to as "nested conditions." Nested conditions will function but conditions that are overlapping will not.
For example, take a look at this provision from a will appointing minor guardians...
In this example, Condition A controls the entire provision and is triggered if Guardian 1 Full Name exists.
Condition B is fully contained within Condition A and is triggered if Guardian 2 Full Name Exists.
This is an example of a nested condition with Condition B fully nested within Condition A.
It's easy if you just keep in mind that:
Nested Conditions are Good: A1 - B1 - B2 - A2
Overlapping Conditions are Bad: A1 - B1 - A2 - B2