Steam a seam does have a very strong bond to the fabric... but it will over time ( and how hot the dryer is) start to come loose. If you are having trouble with the zig zag , do try some inviasble thread. HIGHLY recommend you do a test piece using the fabrics and steam a seam exactly how you will be stitching on the project. This is so you can get the stitch lenght and tensions adjusted before you try it on your project. A stablizer can help keep your stitches where you want them.