I don't work with Windows and haven't used x64bg, but I can try to give some general guidance that should apply regardless of platform and toolset.
When reverse engineering, there often will be very many unknowns and only a few knowns, so stick with what you know. It may also be useful to use your debugger in tandem with a disassembler/decompiler for static analysis, as it may help you orient yourself.
A very important function of the debugger is going to be the "breakpoint". As the name implies, it will break execution at the point you specify. This is how you can stop the program and introspect memory/variables at points of interest.
If the binary is not stripped and you can see function names, you'll want to look for any functions that sound relevant to the operation of interest. Maybe you'll get lucky and there is a function called
extractZip. If so, try setting a breakpoint on this function and step through it by hand once execution is suspended. Static analysis could be really helpful here; even if you don't have function names, you could look for standard library functions being called and break on them, such as
open. You may even see the filename in disassembly if it is hardcoded. Or, perhaps you could identify the ZIP library in use and trace/break in places where it is called.
If you need help using any particular functions of your debugger, there are likely plenty of resources out there to help with that, or a question on Stack Exchange may be appropriate. It may be worth writing your own simple program and running a debugger on it to gain some experience.