I think to get GPS out of the Zeus you may have to enable the built-in GPS in the Zues not using the network GPS. It has been a 3 or 4 years since I've been on a boat with this setup but from memory I think that is the path.
 

If you have multiple grib files the routing algorithm selects a single grib for each data type at every time step.
It looks for the newest - highest definition data for every time step. It does not average the data or pick a single grib for each type.

It is generally recommended unless you have well thought out what you are doing not to load a mix of weather models when doing routing. The results you get might not match your expectations.
 

Not that this is helpful --- but
In tight areas where data is not well modelled the results may or may not be useful...
Having said that --- I have done what you are trying to do. You have to set a very high resolution to get through tight areas.
 

If you are having problems like this with your install best to email Nick directly.

It sounds like you want to ensemble route... If you do a normal route - per step Expedition will evaluate the loaded weather models and use one of them for a given timestep.
In the ensemble route mode the route generates a route per loaded weather model. Note: It is per model not per grib loaded. If you load multiple gribs of the same model they will be combined and prioritised based on the weather model prioritisation rules. (newest highest definition data loaded...)