Gwyneth Paltrow, Chris Martin -- Chummiest Divorce Ever (PHOTO)

Gwyneth Paltrow and Chris Martin vacationed together over the weekend, but there's no getting back together ... they're still getting divorced.

It sure looks strange ... the 2 of them seemed cozy in Puerto Vallarta with Apple and Moses, almost a year to the day since Gwyneth announced their marriage was kaput.

Sources connected with the couple tell TMZ, although Gwyneth and Chris are still friendly, they've been working regularly with a private mediator to hash out the terms of their divorce.

We're told they have been in lockstep, trying to keep things friendly, with no court documents spilling details of the split.