There might be a different approach to try. Certainly, your math skills are strong, but as Diane B said so well, that doesn't mean you have the skills (not the knowledge, but the teaching skills) to teach someone whose math skills are different from your own.
Imagine, for a moment, that your child has cerebral palsy, or another serious mobility issue. You don't have any such disability - you walk, maybe you hike, you can run, and you can use your hands and all your other muscles with ease, without even thinking about it. Does that mean you are qualified to provide physical therapy to your child? Of course not. You, as any responsible parent would, get your child proper help from a qualified health professional who is trained to teach a physically disabled child how to use a walker, how to take steps, how to stand well, how to learn balance, how to achieve their potential in the best, safest method possible. There's a whole science devoted to muscle training, mobility aids, intervention, and all that goes into helping a child achieve mobility and physical independence.
So perhaps your daughter needs help with math from someone who is specially trained to help kids who aren't confident in a certain academic area, or who completely blank when faced with the pressure of a test, or who need a different way to learn. Sylvan, or another similar program, won't undermine your math skills, they will simply help her learn in her different way, or take tests in a different way. They may suggest a quiet private testing area, or their experts may realize that your daughter is approaching math in a different way from your gifted engineering way. It's not a bad thing, any more than the child with cerebral palsy must sit or stand in a different way, using different muscles or aids, from the person who can hop up out of a chair without any difficulty or conscious effort. I'm not saying your child has any disability, but obviously she's functioning differently (not less, not in a sub-standard way) than the way you approach math.