Runtime Analysis – Need for an additional idea to start with the complexity of time

I'm looking at a multi-threaded algorithm, and come to the conclusion:

Work: T_1 = 2 (T (n / 4)) + 6 (P (n / 4))

Scope: Tinfinity = 2 (T (n / 4)) + 4 (P (n / 4))

Note:

P is the proved subroutine with time complexity:

Work: Big-Oh (n ^ 3)

Span: Big-Oh (logn)

I want to take the temporal complexity of this multi-threaded algorithm further, but I do not know how.

Note to all: The master theorem can be used if it is applicable.