If Mark 14:12-16 is from Thursday sundown to Friday late afternoon. Nisan 14.
What does that make Mark 14:17, And in the evening he cometh with the twelve.
Because that is what occurred. "Evening" is not one set time. It is often stayed "between the evenings". We'd say "afternoon".
Here is an example that the 1st Century Jew would follow (it is from the Mishma).
"When the day before the Passover happened to be a Friday, it was slaughtered half an hour after the sixth hour, sacrificed half an hour after the seventh hour, and the Passover sacrifice celebrated (immediately) afterwards." (Minsha)
Now, this reflects 1st Century Jewish thought.
If the Passover happened on a Friday (important because of the following Sabbath) the passover was sacrificed Thursday afternoon.
And this was evening (it was after the sun had reached its apex, but before it had completely set.....between the evenings, which in English is translated "in the evening").
Another explanation is from the Gemara:
"Toward evening,” we know that this religious duty must be discharged
when the sun commences to move towards the west (evening). . . . . Hence this latter was slaughtered half an hour after the eighth hour (two and one half hours after noon); but on the day before Passover, when the paschal lamb had to be slaughtered after the daily offering, the latter was slaughtered an hour sooner. If the eve of Passover, however, fell on Friday, when the paschal lamb must be roasted before the Sabbath set in, the literal text of the passage in the Scriptures is abided by, and the daily offering is slaughtered as soon as the sun commences setting towards the west, i.e., half an hour after noon.
And this makes perfect sence with Mark. And it agrees with the other gospel accounts.
The Lamb sacrificed, two sent ahead to where the passover meal was prepared, and in the evening Jesus came with the Twelve.