Hello aspirant!

Hope you are doing good!

As per your query, I would suggest you to complete your syllabus first. Chances are if you'll start with the lectures alongside your syllabus. You might exhaust yourself and end up not being able to retain anything from either.

You might, however, voluntarily choose to watch few lectures as per your own convenience alongside your completion of syllabus though. (eg. meanwhile you are covering a topic of genetics/biotechnology, you can also watch a lecture related to the same)

Moreover, NEET (UG) is scheduled for July 17 2022. If you are successful in completing your syllabus by 10th of May, I'm supposing you will be having enough time to watch the lectures afterwards. Make sure you don't exhaust yourself out in the process. Take it one step at a time. And remember, consistency is the key. Revise your syllabus and stay confident with what you've prepared.

Good luck!