Your fastest option is to return to your old university and complete your engineering degree there. I’ll explain why, and some other issues, in a moment, but this should be your fastest option. Know that graduating with a degree in engineering does not mean you need to work as an engineer. A degree in engineering will make you hirable to companies with strong finance training programs (due to your math skills), to being able to teach math or science at the K-12 level (with some additional steps required), and to take the actuarial science exams. The most lucrative option of those, if you’re interested, is becoming an actuary. In demand, good pay, and usually relatively reasonable hours. My friend is one, loves it. Might be worth considering.
In terms of other majors that might maximize your current credits/minimize your time to graduate, I’m thinking physics may be an option. In my experience, this tends to be the major that, at many schools, has the most overlap with engineering. But you’ll need to sit with an advisor at a school once you’re admitted to really figure out the details of this and other majors. Until then, you might to go the website for a college you like, and start looking at the course requirements for some of the majors you might like or suspect might work for you, and see what overlap you may have.
Some other things to think about, relative to what you wrote:
Due to the rigidity of most associates degree programs and how your existing credits might transfer, it’s quite possible that it will take you just as long to complete an associates as it would to finish a bachelors. So my first suggestion is that you focus on bachelors programs for now, as that may give you the most bang for your buck.
Since you were last in college in 2000, it’s possible that some universities would require you to retake some of your old classes, even if you were to major in engineering, since your credits are so old. Are you near your former university, or do they offer online degrees? I’ve seen many unis reaccept students who’ve left, and because you’re continuing on with them, not age out your old credits. This is why I suggested that the fastest route to a degree is to return to your old uni, if that’s possible. This is a question you’ll need to ask all future colleges when you talk to them - how old is too old re: credits in terms of transferability.
If your old credits are still “good”, the most unis will require you to spend a certain amount of time with them in order to earn a degree there. This time varies from 12-24 months. So this is also something you’ll need to look into with each college as well.
If you find a school that will take all your old credits, they may not accept them as you’d like them to be accepted in terms of fulfilling a specific major, even if that major is engineering. So even if you have three years done, you may find that you end up with two more years (as an example) because of how your credits transfer in. Know that they can’t tell you exactly how your credits will transfer until after you apply, get in, and they do their formal transfer credit evaluation, but you can ask questions like how generous they tend to be re: transfer credits.
Some unis are way more generous re: transfer credits than others are. You’ll need to dig and also talk to admissions to find those near you that work to maximize this. Some come right out and tell you on their websites; others, you’ll need to talk to.
So for now, if you’re near your old uni, I’d suggest you contact them first. They’d probably be your fastest option to a degree. If they aren’t near you, start looking at local universities - at bachelors programs, as, again, it’s likely going to take you just as long to finish a bachelors as to do an associates - so look at a bachelors. At each uni, ask about age of credits, majors that are likely to be closest to engineering in terms of overlap of courses, the amount of credits you must earn at their uni to graduate from there, etc.
