So I have the Dell Inspiron 15R which has an AMD 7670m and an Intel HD 4000. I know that AMD discrete GPUs and iGPUs can be in hybrid crossfire. My question is that is it possible to do the same with the AMD 7670m and the Intel HD 4000
The only way to do that with an Intel HD4000 is using Lucid Virtu. You laptop is most likely compatible with that software BUT only certain intel chipsets are "LICENSED" meaning that if you do not have one of the "supported" chipsets then LUCID Vitru will expire after 30 days.
With high end graphics cards the virtu softwares hyperformance mode is not a big deal but I am guessing that with laptop graphics cards it may actually help.