Growing competition from Microsoft Teams, coupled with a tough macroenvironment, could lead to even more pain for Zoom Video shareholders, according to Citi. Analyst Tyler Radke downgraded Zoom to sell/high risk from neutral/high risk. He also trimmed his price target ahead of its earnings report next week . "Zoom's post-COVID growth trajectory has always been more challenging, given pullforward dynamics, but we see new hurdles to sustaining growth including rising competition (MSFT/Teams), macro-related weakness hitting SMB and less critical spending categories and margin risk," Radke wrote in a Tuesday note. "Although new SKUs such as Phone are promising, we believe increasing churn in SMB/online, and rising competition in Enterprise will more than offset new product strength and drive estimates below consensus," he added. Shares of Zoom struggled this year as the video teleconferencing company failed to sustain momentum from its pandemic highs, when Americans adopted the software to remotely attend meetings. The stock is off 38% this year and more than 68% below its 52-week high. Radke expects the stock will fall further from here. The analyst lowered the price target to $91 from $99, implying nearly 20% downside from Monday's closing price of $113.23. Shares dropped more than 3% in Tuesday premarket trading. "We are making significant estimate cuts with our revised revenue and FCF estimates 8% and 17% below the street in FY24E. Our model forecasts revenue growth slowing into MSD next year, with FCF declining as a result of ongoing investments and working capital. We believe shares have downside given the +43% move off recent lows and trading at 21x our revised FY24 EV/FCF estimate," he added. Still, Morgan Stanley analysts considered Zoom favorably ahead of its earnings next week, citing operating leverage "likely to drive upside on bottom line even as growth normalizes post-COVID." —CNBC's Michael Bloom contributed to this report.