Send it at their midnight, not yours
If they are three time zones ahead, send it when their clock turns. You can write the note hours earlier and hold it, or just stay up. Either way the message arrives inside the moment rather than hours into the new year.
This is the one occasion where the timing of the delivery is part of the gift.
What to send
New Year is a fresh-start occasion, so the bright flowers fit: a sunflower for the plain joy of it, or a tulip for something lighter.
If the year that is ending was hard, do not send yellow. A magnolia or a lily acknowledges the difficulty without turning the message into a demand for optimism.
What to write
Avoid predictions. “This year is going to be your year” is a promise you cannot keep, and it puts pressure on someone who may already be dreading January.
Write about the year that ended instead. Name one thing they got through, and say you are glad you were around for it. That is more honest and it will be remembered longer than any resolution.