There's a lot of noise and confusion about what exactly "zone 2" is and why. But definitely longer easier (you're not out of breath) runs build a foundation in more ways than just your cardiovascular system. It's those other components that take a longer time to build. The key is that you are not over-training (watch your sleep and joint pain as an indicator) and can recover and that you are progressively increasing your load by lessay ~10% distance a week. Easy system would be 2 shorter runs and one longer run a week.

There are plenty of online training program generators that are pretty good and will take you from zero to running 10k. I used an online program to run my first 10k somewhere circa 1990.

There a lot of more cutting edge science online (and I follow Nick as well) but if you're not a competitive athlete and are just trying to get in better shape then the answer is mostly just do it. Over some base of running you can throw in some interval training including HIIT.