Why does the current not skip resistors R3 and R5 when R6 and R4 have no resistance?
With R4 and R6 being zero, this means they are essentially a short circuit. You should imagine the initial circuit to look like this:







simulate this circuit &ndash; Schematic created using CircuitLab

This now becomes much easier to visualise.


  however when I solved it I just took out the R3 and R5 so I got a
  different answer for the current flowing through the voltage source


I believe what happened here is you mistook the meaning. Where you removed them from the circuit, what you should have done is just replaced them with a wire as shown above. When you do this, you can see that R3 and R5 are connected straight across the supply voltage, so there must be current flowing through them. From here, you can re-draw and simplify the circuit to solve.