Zippers are hard to insert. Yes it's true. So if you fear them or avoid them altogether you are not alone. But you can learn to love them, or at least live with them.
There are a million blog posts and Youtube videos out there telling or showing you how to insert a zipper. You can read and watch them all, but really one or two will do because the best way to learn is to just do it. Lots. And in a garment too, preferably one that's sturdy enough to take a lot of unpicking. Practising on scraps is fine too, but you won't really be replicating the terror that is an almost finished dress (all that fabric! all those seams that need to line up! and yards of fabric to keep out of the way!). Suddenly what seemed easy in calico/muslin just ratchetted up a factor of 10.
So, my advice is don't avoid zippers, and don't beat yourself up about them - they will get easier with practice.
What else can help? Having just taught some lovely students (who were sewing up a storm until we hit the zippers) I realised part of it is just the associated fear, but these tips may help:
1. Get really good at sewing straight first. If you are having trouble sewing a straight line on a normal seam, you're in trouble.
2. Try a lapped insertion - I find it much easier than the standard centre seam style, and it's a beautiful retro finish. In fact, I think I'll post some instructions on this soon....
3. Go slow and hand-baste at every step! We all love to get it done fast, but I find that as soon as I start thinking "this is going swimmingly well! I should be done in no time!" - as soon as I think that I make a stupid mistake that sees me spend the next half hour unpicking...
Vintage patterns often just say 'insert zipper according to instructions on the packet'...ummm what packet? They don't come in packets anymore and definitely not with instructions! Modern vintage repro patterns aren't much help either as they generally instruct you to do a centre seam insertion - which is not terribly vintage nor easy in my book. The best instructions I've found are in vintage sewing books, so try and find one published around the time of the patterns you like to make.
Zippers can be beautiful and because they are difficult, you'll be so proud of the ones that work well. So don't give up!
What's your zipper tip?