For example, in block 5 now (GI), how do I isolate cards from Zanki or Duke pathoma decks into a smaller deck so I can use it for class. Or even if I watch a video, and then want to do those specific cards after.
Search "Anking" on youtube, specifically the hierarchical tags video. I have Uworld open so I can't copy and paste. Basically that add on helps make your browser a little bit better to navigate. His videos are super helpful for the entire anki software.
The short answer to your original question would be to create a new deck and title it something like "(school name) GI Course" and then open up the deck that you want to pull cards out of (Zanki GI Pathology, for example), once you click that deck, hit the B button to open up the browser, and then enter. to see all the cards. Then you can sort through them and CTRL click on each ones you want to move. Then, after they're highlighted, you click the "move cards" and it should open up options to pick which deck to move it to. But be aware, moving cards around can be an easy way to lose your original organization of the Zanki master deck.