Since your TPS and EAD is pending, you can withdraw it anytime but again are you sure that your company has a good success record of I-140 approval. If you are confident about the I-140 approval, then withdrawing TPS and EAD is the best option. You will be in problem if your TPS-EAD is approved before I-765 (EAD through GC ). So, better talk with the company lawyer and also get second opinion through your own lawyer. Get 30 mins legal service from any good immigration lawyer. Since TPS is involved, talk to Nepali Lawyer in New York. They know better about TPS-H1B-GC situation.