I'd remove the plants and replace them with rocks. The mbuna will just eat or dig up the plants anyways.
Labidochromis caeruleus-great fish, fairly peaceful by mbuna standards. M/F ratios don't matter.
Pseudotropheus demasoni-these are great little fish too, however, they are best kept with either a single speices, or groups of 12 or more. They are extremely aggressive to their own kind (hence the group of 12+) and other fish that look like them.
Sciaenochromis ahli- This is a hap, needing different feeding requirements, and will grow too large for your tank.
Pseudotropheus zebra-This is actually a generic name give to several different species. The most common are metriclima estherae (females are orange-red, males are a yellowy-orange) and metriclima callainos (both males and females are blue). Both of these species have similar temperments, they are a bit more aggressive than l.caeruleus, should be kept with 1 male to 3-4 females.
Melanochromis auratus- extremetly aggressive, IMO should only be kept in a species-only tank.
Pseudotropheus lombardoi- Another very aggressive fish, again, should either be kept alone, or in a very aggressive set up.
Stocking suggestion:
You should be able to comfortably house 12-15 adults in your tank. I have two stocking suggestions.
#1
4-5 Labidochromis caeruleus - m/f ratio not important
4-5 of either m.estherae, or m.callainos, 1m/3-4f
4-5 of another mildly aggressive species
#2
12 p.demasoni - m/f doens't really matter in larger groups, but you may need to remove additional males once they reach maturity and add females in their place.
5 l.caeruleus - m/f ratio doesn't matter.
The reason you can have more fish in option 2 is because demasoni are so small.
Or you could always to a species only tank of either m.auratus or p.lombardoi.