When I go zerg on an island by BO is usually 9 dronesoverlord
spawning pool followed by drone before overlord finished
extractor before spawning pool finished3 sunkens (VERY IMPORTANT) 
new hatch and upgrade hatch to lair at same time.(constantly building drones)
when enough for hydra den build one and about 3-6 hydras 
build some spore colonies arround base for a good defense. 
by this time the lair is up and i build a queen nest and spire at the same time
build up several mutas for a rush (if I feel so inclined) and 
hopefully my partner is also ready for a rush)
upgrade overlords for speed and carrying upgrade to hiveupgrade spire
At this point is where the good stuff starts. 
You are going to want multiple outposts, so you upgrade the overlords 
and move on outThe fastest way to do this is the following. 
Get like 3 overlords with 2 drones in each. 
Send each to a different island and drop the drones
build a hatchery and extrator with the two drones
at your main base make tuns of drones and start a nydus canal for 
each expansion. 
when the hatcheries are finished send a nydus canal to each one and 
send the already made drones on over. 
(this is also helpful for defending against attacks with hydras.
While doing all this you are going to want tuns of mutas. I know many 
people are going to complain about this part but please hear me out
keep 12 mutas strictly as mutas, they are good against wraiths, BC's 
and carriers, although carriers in numbers will get a good chunk of 'em. 
get a bunch of devs, they kick against corsairs, valks, carriers (not 
as much), and are okay vs BC's. 
keep about 7 extra overlords and send them into the fray, they are a 
must vs cloaked units. 
As this is an island map get guards and take out their defenses. 
support the guards with devs and some mutas to be anti air. scourges 
rule the skies, so attack with them and take a chunk out of your 
enemies air forces. If you are vs protoss the first thing you should 
do is this.  KILL CORSAIRS with devs!!!  If they have templars TAKE 
THEM OUT WITH ALL POSSIBLE SPEED! Spread out your mutas and come at 
them from all sides if you haven't any guardians handy, if you do 
guards take them out in 3-4 hits max. as a sneak attack fill several 
overlords with hydras (or whatever your preference) and attack their 
base with air while delivering the present under cover of fire. 
Also if attacking protoss take out the pylons to their starports 
followed by the pylons powering the gateway and robotics factory. 
Since you should have taken out the towers you should have no trouble 
finishing them off. Once their defence is diminished take a second to 
rebuild your forces.
If you are against terran again take out towers with guards. valks 
with devs bc's with mutas and scourages and once thier defence is 
down the first order of business is the add on attached to their 
starport. marines go down fast so don't worry about them, but take 
out the factory asap, goliaths can hurt you. 
Also broodling is your best friend.  Used on goliaths it can destract the other goliaths 
long enough for your other queens to brood the next one.  Same 
consept works on dragoons, and most importantly templars.