Simultaneous I-140 Portability and H1B transfer

[Chinar]

Hi, does anyone know what is the process for porting over the I-140 to a new employer. Any specific forms that need to be filled or documentation required.

Can one do a H1B transfer and 140 transfer at the same time with the same employer. Do both need to be done at the same time or I must wait when H1B transfer completes and then port over the I-140 once I have joined the new company's payroll.

[Chinar]

Can anyone help answer my query. I have H1 as well as EAD that I have not used yet. I have an offer from another employer. I want to retain my H1 and also transfer my GC to the new employer. Do I need to transfer the GC first followed by the H1 or the other way round.

Any help that you can provide would be much appreciated.

Regards,