Thanks for posting your query.
It hardly matters whether you take before, after or same time.
You can take as per your comfort but observe the dose schedule.
It is not rule that taking nitrofurantoin
will cause fungal infection
If you do not have a fungal infection already then you really do not require fluconazole
Hope I have answered your query.
If you have any questions I will be happy to answer.
Please close the query if you have no other questions.
Wish you a good health.