The stock market can't seem to decide which way to go, and that's made September a bumpy month for the Nasdaq Composite (NASDAQINDEX:^IXIC). After it posted a significant gain Tuesday, investors were less confident in the benchmark's prospects on Wednesday. By around 3:30 p.m. EDT, the Nasdaq was down almost 3%.

Many investors had hoped that Tesla (NASDAQ:TSLA) might be able to spur another rally in the Nasdaq on Wednesday, with its Battery Day event having occurred late Tuesday afternoon. That proved not to be the case. However, Zoom Video Communications (NASDAQ:ZM) managed to keep up its end of the bargain, helping to offset losses from other tech giants.

Tesla's long-term strategy

Tesla shares were down another 10% on Wednesday, adding to losses from Tuesday's session. As CEO Elon Musk had suggested might prove to be the case, investors weren't satisfied with what Tesla revealed on Battery Day.

Blue Tesla Model S on a road near sunset, with water landscape nearby.

Image source: Getty Images.

On its face, what Tesla's trying to achieve makes perfect business sense. Musk is looking to bring battery production in-house in order to scale up to the volumes necessary to bring costs down. Much of the reason why Model 3 electric vehicles are as expensive as they are is because the batteries necessary to drive propulsion are costly. By being more efficient with batteries, Tesla hopes to cut the cost of its vehicles to $25,000.

Yet some had hoped that Tesla would have news on the much-anticipated million-mile battery. That wasn't forthcoming, and the less impressive incremental progress that the automaker has made wasn't enough to justify another move higher for the stock price in many people's eyes.

Few dispute Tesla's leadership in electric vehicles, and the company continues to achieve amazing things. Yet shareholders now have such lofty expectations that even good news isn't always good enough to move the share price higher.

Zoom-zoom

Meanwhile, Zoom Video Communications' shares climbed 2%. The video-collaboration stock had been much higher earlier in the day, but the afternoon downdraft weighed on its gains.

Zoom's stock has found itself tied to the changing fortunes of the COVID-19 pandemic. Health officials are increasingly concerned that as summer gives way to fall and winter, the Northern Hemisphere will once again see greater incidence of the disease.

Already, hundreds of millions of people are using Zoom as an alternative to in-person contact, whether it's in the business world or in education, government, or social groups. As the pandemic goes on, those who've held out on Zoom will be more likely to start using the service. Moreover, those who've used free versions of Zoom will consider paid subscriptions, boosting revenue.

Everyone understands that Zoom's growth isn't sustainable in the long run. But the longer Zoom can keep up the pace, the more its share price will be able to climb. In the end, that might prove essential not just to Zoom's run to record heights but also for the health of the Nasdaq more broadly.