External thunderbolt 3 gpu and internal conflict
I have a laptop with a 1060 that preforms fairly well for what it is. I just got a bizonbox 3 external enclosure and put a 1080 in it.

Windows is able to utilize the 1080. Hashcat does not see either gpu once the external one is plugged in. However if I disable the internal card after plugging in the 1080, Hashcat will see the 1080 and can crack with it.

So I can get Hashcat to use both cards but currently not at the same time. Is there anyway to look into this to allow for both cards to be used at the same time.

I don't have a solution for you, but man is eGPU via Thunderbolt a bag of hurt.  None of them "just work", especially if you're on a Mac.  Which is even more ridiculous since Apple have been championing Thunderbolt for a long time now.  Intel has been demonstrating eGPU since LightPeak days.

Try egpu.io and the tech inferno forums.  Might try netkas.org as well.

Let us know how you make out.