Improve it in what way? What type of trouble are you having?
In terms of prep, you would normally need to oxidise sulphides to oxides (either by roasting or with HNO3) before dissolving further with acids. Otherwise you could try a Na2O2 fusion and subsequent dissolution...possibly the best option if you want total dissolution particularly for Al. Then I would try Al 394.4nm, Pb220.353, Zn206,2 or 334.5nm and Fe259.94 but the best line will depend on the concentration you are expecting. The roasting will lose your S, so possibly fusion is the best route in that regards too. S182.034nm line usually most successful. If your lead concentrations are very high and you used HCl, be aware that the Pb will precipitate out of solution unless you use a high dilution or a significant excess of HCl. When calibrating, keep the sulphur in separate calibration standards or it may come out of solution as a sulphate of one of the other metals. If you are getting calibration line curvature try jacking up the plasma power of using a less sensitive emission line. internal standardisation will help you to improve precision, maybe Y or Sc or Lu, but scan your samples first because you can't use an internal standard that already has variable concentrations in your sample.