I'm taking 5mg of finasteride per week(not in once of course!)
I've been using Zinc for two weeks now (25mg once a day which is high dosage) and I'm almost sure that my libido has increased.
What is for sure is that I have morning woods more often and that I also sometimes get random erections which I used to have before starting finasteride.
Also, Zinc is good for hair, skin, and assimilation of other vitamins in your body(yes, it's pretty useless to take other vitamins when you lack of zinc).
Plus, it's pretty cheap so go now to a drug store and get some, try it 2 weeks and see if it helps.
Good luck