I'm pretty sure the LSZ-1 machine makes a significantly smaller zig zag than the more expensive industrial machines used to make most of the commercial sails. I'm not sure how significant the stitch size is in sailmaking and repairs.
Not having made sails, the following is academic. The LSZ-1 zig-zag width is 5 mm. James Grant's Sailrite sail construction series states that the zig-zag stitch should be 3/16" (or just about 5 mm.) The Sailmaker's Apprentice doesn't seem to mention an optimum width, but it's about 500 pages so the width might be in there somewhere. Don Casey in This Old Boat recommends at least 6 mm.
However, too wide of a stitch could be a snag problem.
While not stated, these widths are probably for two-point, single-step zig-zag. Multi-point, multi-step zig-zag could be wider without the snagging problem. For example, the maximum width for the Sailrite professional, a four-point, three-step machine, is 10 mm.
The widest two-point, single-step zig-zag I've seen is 12 mm for the no longer marketed Sailrite Sailmaker which was based on the Brother TZ1-B652 and has separate feet, feed-dogs and throat-plates for straight-straight-stitch, 5 mm zig-zag and 12 mm zig-zag