Max Verstappen topped the timesheets earlier, out-pacing Valtteri Bottas by 0.556s and title rival Lewis Hamilton by 0.794.
Of course, the Red Bull driver benefitted from an exquisite, and seemingly unplanned, two from teammate Sergio Perez, but even so that is quite a gap.
The Mercedes pair, particularly Hamilton can be expected to raise their game in qualifying, but even so, that's a mighty ask.
On the other hand, though qualifying pace appears to be Red Bull's advantage, Mercedes seems to have the upper hand in terms of race pace.
Behind the big two teams is anyone's guess, with Alpine, McLaren and Aston Martin looking strong, and while Ferrari was quickest yesterday afternoon, the Italian team struggled earlier, a situation not helped by Carlos Sainz crashing out at Turn 3.
Pierre Gasly is looking good, while Nicholas Latifi continues to show good progress, suggesting that both Williams could make it to Q2 this afternoon.
All three sessions have seen red flags, be it down to technical issues or crashes, and there is no reason to suspect that this won't be the case this afternoon.
Zandvoort is turning out to be one of those tracks that punishes mistakes and leaves little room for error... indeed the unforgiving run offs have seen few, if any, drivers punished for exceeding track limits thus far.
Half an hour before Q1, Mattia Binotto is unsure whether Sainz' car will be ready in time for Q1 On the other hand he confirms that the Spaniard's gearbox is fine.
With an eye on the engine issues encountered by Vettel and Hamilton yesterday, all the Mercedes-powered teams are using their 'freshest' power units, those that have completed the least mileage.
In an effort to close the gap to Verstappen, the Mercedes crew have been working on Hamilton's car throughout the break.
Ahead of Q1 the air temperature is 18.5 degrees C, while the track temperature is 35.3 degrees.
Of course, as we have seen over the previous sessions, traffic is a clearly problem here and consequently we could see a number of surprise eliminations in the next 18 minutes.
George Russell warning that the increasing wind could cause problems.
The lights go green and Mazepin is first out followed by his Haas teammate, Latifi, Tsunoda and Kubica.
Schumacher gets things underway with a 12.741 but this is instantly eclipsed by Tsunoda (11.947).
The crowd rises as Verstappen heads out.
Latifi posts an 11.699.
While Verstappen is on softs, the Mercedes pair head out on mediums.
Perez goes quickest with a 10.700, but moments later Verstappen crosses the line at 10.036.
As Giovinazzi goes third, Sainz heads out.
On the mediums, Hamilton posts a 10.183 - just 0.147s off the pace - while Bottas posts 10.449.
Gasly goes third (10.274), ahead of Leclerc and Bottas, Perez and Giovinazzi.
As Alonso has a small lock-up, Russell is told to work both axles on brakes.
Alonso goes fifth with a 10.435 but is demoted when Bottas improves to 10.219. "Good lap," says the Spaniard.
Hamilton also improves, closing to within 0.078s of Verstappen with a 10.114.
Showing no ill effects of his earlier crash, Sainz goes 8th with a 10.537.
With 5:45 remaining, both Aston Martins are in the drop zone, along with Kubica and the Haas pair. Russell, Ricciardo, Giovinazzi and Ocon are hovering.
Sainz advised that a "big" track evolution is expected.
Vettel crosses the line at 10.731 to go 13th, as Russell posts a 10.382 to claim 5th.
Stroll remains 16th, despite improving to 10.821.
Ricciardo is unsure whether he needs less front wing as he slips to 17th.
Hamilton and Bottas head out on fresh softs as all bar Verstappen, Gasly, Russell and Alonso are on track.
At Turn 13 there are 7 or 8 cars looking for free air.
Leclerc goes top (8.829) and Sainz second while Giovinazzi goes fourth with a 10.050.
So the track is evolving.
Ocon goes sixth, Latifi fifth, while Norris can only manage 15th.
A late improvement sees Ricciardo go ninth.
Vettel fails to improve after being impeded by both Haas drivers. "That was terrible," he is told.
The big shock is that Perez has missed the cut.
As it is confirmed that the Vettel/Haas incident will be investigated, Leclerc is quickest, ahead of Sainz, Verstappen, Giovinazzi, Latifi, Hamilton, Ocon, Bottas, Ricciardo and Gasly.
We lose Perez, Vettel, Kubica, Schumacher and Mazepin.
Latifi is first out for Q2, followed by Verstappen. Russell and Norris are next out.
The Mercedes pair head out, like the rest they are on softs.
Latifi sets a benchmark 11.161, but Verstappen responds with an eye-watering 9.071.
A 10.332 sees Russell go second as Norris can only manage third (10.406).
Bottas posts 9.769 and Hamilton 9.726, both over 06s off Verstappen's pace.
Giovinazzi posts a 10.033 to go fourth.
"It's so tricky with the wind," warns Russell.
Leclerc goes second (9.437) and Gasly third (9.541).
A 9.865 sees Ricciardo go sixth, ahead of Sainz, Ocon and Alonso.
"Good lap, mate," Gasly is told.
With 5:30 remaining, Russell, Stroll, Norris, Latifi and Tsunoda comprise the drop zone.
The Williams pair have the track to themselves, however Russell is off at Turn 13 and lightly brushes the barrier after carrying too much speed into the corner.
"I'm sorry guys," he says as the session is red-flagged.
The youngster is able to drive back to the pits, as he admits that "I pushed it too hard".
The clock stops at 3:53.
Ahead of the green light, Russell climbs back into his car, then promptly climbs out again. "The car is OK to continue," says Williams.
Meanwhile, the barrier is repaired and gravel swept from the track.
In the Alfa Romeo garage, mechanics are swarming over Giovinazzi's car.
Latifi heads the queue at the end of the pitlane as the session resumes, with Verstappen right behind. However, Russell is out of his car, his session now clearly over.
Oh dear, in another incident, Latifi is off and in the barriers at Turn 8.
He dips a wheel on the grass exiting Turn 7 and then appears to be distracted by Hamilton going into Turn 8. In passing the Mercedes he once again dips a wheel on the grass, as a result he's off and into the barriers. It's a big impact.
The session is red-flagged again and will not resume.
Quickest is Verstappen, ahead of Leclerc, Gasly, Hamilton, Bottas, Ricciardo, Sainz, Ocon, Alonso and Giovinazzi.
We lose Russell, Stroll, Norris, Latifi and Tsunoda.
Check out our Saturday gallery from Zandvoort, here.