If you want to bring magma up 4 zlevels down to the surface, you need three things:
1) A moat for it to fill. Easy enough.
2) A knowledge of how screw pumps work. It'll be easier if you create a screw pump tower so that they can transfer power amongst themselves:
sP_
_Ps
sP_
_Ps
~
Where _ is a floor, ~ is your liquid of choice (magma), and sP is a screw pump, where s is the source (pump from) and P is the target (pump to). I can't show it on the forum here, but there should be no floor under the s portions -- that's where the power transfers. Check the wiki for more details.
Due to the vagaries of the game, the screw pumps do not need to be magma safe, as long as they are not themselves immersed in lava (it can touch the P portion, where the lava comes out, but lava cannot touch the s. Since screw pumps typically pump from a level below, this is usually not a problem.)
3) A way to power the pumps. Dwarf power could be used, but may cause heat-related deaths. Waterwheel or windmill power is better. If the pumps are stacked correctly, you only need to get power to one of the pumps, and the power will go through the other ones.
4) Optional. A way to drain the moat. If you have a bottomless pit or chasm, that's ideal. Otherwise, you could drain it into a cistern (if you have water available) and make obsidian in the bargain, too.
Draining is easiest if you have iron and bauxite -- make floodgates/raised bridges out of iron, and use bauxite mechanisms when connecting them to the levers. If you don't, you can still use screw pumps -- set up a screw pump so that it feeds from the moat, and into the beginning of your drain, whatever it may be:
sP
~XX