Going to try this again.
I would recommend double stitching the handles in place before placing the zipper and stitching it.
I have also seen zippers done so that they are a short way down below the upper edge of the tote and the handles stitched in such a way that they are attached to that 3/4" - 1" inner edge as well as to the seam with the zipper.
Both of these methods will help keep the handles from pulling out along the zipper.
Oh, and if you use the webbing for handles, be very sure to singe the cut ends thoroughly to melt the loose fibers together or the ends can fray horribly (ask me how I learned this!)