After an uneven debut season that hinted at Zhou's underlying promise, the Chinese driver was retained for a second season and immediately got off to a stronger start. While he was behind Bottas in Bahrain, Zhou qualified and finished ahead of the Finn in a difficult race for Alfa Romeo in Saudi Arabia.
When both drivers struggled with unexpected balance issues in Melbourne, Zhou outqualified Bottas again and then went on to take his first points of the campaign with a ninth-place finish, the second points haul for the Sauber-run squad after Bottas' eighth place in Bahrain.
Alfa Romeo's head of trackside engineering Xevi Pujolar has praised Zhou for the steps he is making in his sophomore campaign.
"I think Zhou is raising the game. And I would say now they are both quite even," he said.
"That's good for us. Qualifying [in Australia] was not ideal, but in the last two qualifying sessions they are close to Q3, both of them and that's good for the team."
From the start of winter testing Zhou made a markedly more assured impression and in Melbourne he said that "it's good to be feeling confident for the first race of the year which I wasn't last year this time."
Pujolar thinks that this increased self-confidence is the main factor behind the 23-year-old's vast improvement.
"He's more confident," he said. "The car is a different car but in Formula 1 with the tyres... even the tyres have changed a bit, but still it's the same with the team.
"And then working with Valtteri as well and that's how we can [make steps] with both drivers together. And it gives himself confidence as well."
Before scoring his first points of the season Zhou, who benefitted from Melbourne's chaotic race of attrition, felt Alfa Romeo was close to getting into the top 10 on merit, but that small details are decisive in the tight midfield battle.
"It’s clear there are three or four teams clearly ahead of the rest – but then I think from P8 downwards it is very tight," he said. "Everybody can be grabbing these final points finishes, which is the target.
"We're not too far away from this. So it's just the little details that can really make the difference in the midfield."
