回複：小白兔，Pjiang老師, please clarify 180 days issue

First, make sure you have an approved I-140 to avoid the risk down the road that its denial will lead to the denial of I-485. You can then safely change employer after your I-485 has been pending for more than 180 days and the new job falls under the same or similar occupational classification. If you meet these requirements, the subsequent withdrawal of the I-140 petition by your former employer will have NO impact on you.