Both CPUs are old. I5-4670 is 5 years old and i5-6402P is 3 years old.
The prices of both brand new are very high. There are cheaper and more powerful current CPUs.
As they said before, both need different motherboards.
They also need different DDR memories. i5-4670 (DDR3 / DDR3L) and i5-6402P DDR4.
Can you tell us if you already have mobo or memory and the price that you request for these CPUs?