On the third attempt Palace were able to get past the competition's meanest defence as two goals from Ismaïla Sarr saw the Eagles come through the tie, via extra-time.
That means a place in the last eight of the tournament, with the quarter-finals set for next month.
But what else happened on Thursday night as the last 16 came to a conclusion...
#### **Fiorentina set up South London visit**
They may have struggled in Serie A this season, but Fiorentina are once again saving their best performances for the European stage.
La Viola reached a fourth successive quarter-final in this competition despite an early second leg scare against Polish side Raków.
Leading 2-1 from the first leg, Fiorentina fell behind on the night when Karol Struski drilled a finish beyond Oliver Christensen.
Roberto Piccoli headed against the post for the visitors, and then equalised in fortuitous circumstances when Cher Ndour's effort deflected off him and into the net.
But they had to see out a nervous final 20 minutes as Raków pushed forward in search of a leveller. The home side were then punished for overcommitting in the closing stages, With every Raków player up for a late corner, Marin Pongračić managed to convert from his own half and set up a meeting between the two-time Italian champions and Palace in the next round.
AZ Alkmaar have already visited Selhurst Park in the league phase of the campaign, with Palace winning 3-1. But a potential rematch is still a possibility after the Dutch side saw off Sparta Prague in the last 16.
The tie was firmly in the balance after AZ snuck a closely fought 2-1 advantage following the first leg.
But they produced one of their best away performances of their season to make light work of a side who played Champions League football last year.
Isak Jensen opened the scoring with a smart finish just eight minutes in and from that moment AZ never looked back. The in-form Troy Parrott got the second after the break, before further goals from Sven Mijnans and Ro-Zangelo Daal gave them a 6-1 aggregate win.
AZ will now face Ukrainian side Shakhtar in the quarter-finals. They held on to reach the last eight despite a 2-1 home defeat on the night against Lech Poznań.
Overall Shakhtar came out on top 4-3 on aggregate. The winner of that quarter-final will face the winner of Palace-Fiorentina in the semis.
**Every result from the UEFA Conference League Round of 16 second legs**
* Rayo Vallecano 0-1 Samsunspor **(Rayo Vallecano win 3-2 on aggregate)**
* Shakhtar 1-2 Lech Poznan **(Shakhtar Donetsk win 4-3 on aggregate)**
* Sparta Prague 0-4 AZ Alkmaar **(AZ win 6-1 on aggregate)**
* Strasbourg 1-1 Rijeka **(Strasbourg win 3-2 on aggregate)**
* AEK Athens 0-2 CM Celje **(AEK Athens win 4-2 on aggregate)**
* Mainz 0-2 Sigma **(Mainz win 2-0 on aggregate)**
* Raków Częstochowa 1-2 Fiorentina **(Fiorentina win 4-2 on aggregate)**
* AEK Larnaca 1-2 Palace **(Palace win 2-1 on aggregate)**
**Quarter-final ties** (to be played April 9th and April 16th)
* Shakhtar vs AZ Alkmaar
* **Palace vs Fiorentina**
* Rayo Vallecano vs AEK Athens
* Mainz vs Strasbourg