It isn’t an exact science, but it’s generally accepted that you want to be drawn as the away team in the first leg of a European knock out tie.
The effects of that may be limited just now due to a lack of fans in the ground, but a positive result away from home is always going to give you a huge advantage in the home leg.
If you’ve managed to get some away goals then it can force your opponent to overcommit to attacking and they can be picked off, while you also get extra minutes in a familiar ground if it goes to extra time.
Arsenal and Spurs can’t play at home on the same day in the Europa League even if they draw set up that eventuality, so it appears that Arsenal’s FA Cup triumph has come good for them again:
Tottenham's Europa League tie will be reversed, they cannot play at home on the same day as Arsenal, per UEFA rules (not day switch).
The national Cup winners (Arsenal) hold the fixture rights.
Spurs v Dinamo Zagreb
— Dale Johnson (@DaleJohnsonESPN) February 26, 2021
Spurs will feel like they should be beating the Croatian side but it will be a tough test, so they would surely prefer to get that home leg out of the way to begin with.
If it is tight and they end up going out after losing the second leg in Croatia then you could suggest that this ruling played a part in the result, and it means the FA Cup win would bring Arsenal fans a little extra joy when it’s not expected.