There is no other way than to reduce body fat and at the same time do ab work out. Kick boxing or boxing works great as abs are tigth throuughout the entire work out.

Achieving the 6 pack is all about lowering bodyfat - which is different to losing weight. I reached my goal weight and no sniff of a 6 pack in sight. 3 months later I'm back at that same goal weight after a mini bulk & cut but now I have about 5lb more muscle and 5lb less fat, so the abs are much more pronounced!

You'll still need to create a deficit, be it through diet or cardio or both, but you'll also need to focus on making sure as much of the tissue burned through your deficit is fat and as little lean tissue as possible.

Add or keep some resistance training in your routine and keep it heavy. On a deficit this serves to maintain muscle rather than building it so much. Your body will find it difficult to burn lean muscle tissue when you're forcing it to repair and adapt. Keep working on the abs but there's really no need for 200 crunches a day or anything silly like that, just get a solid core workout every other day.

For nutrition, read into how different foods and food type combinations are metabolised into adipose tissue (that's a whole thread of it's own so I won't ramble on about it here) and adjust your eating to ensure as little as possible that you eat has a chance to be stored as fat. Keep your fats relatively low and particularly keep your sat fat very low (no more than a third of your total fats). Keep your protein high but space it all out a bit, particularly getting a chunk of your protein somewhere near your resistance work to make sure it's used for the right thing.

Carbs are a debateable subject... Me, I'd try and make sure you're not getting more carbs than protein as a guide, but that's up to opinion…

Hope some of that helps.

Jay