The past year has been miserable for many investors. Economic uncertainty has driven the S&P 500 into a bear market, and many growth stocks have lost more than half of their value. For instance, Airbnb (ABNB -3.66%) and Zscaler (ZS -1.82%) have seen their share prices plunge 56% and 67%, respectively, leaving both stocks near a 52-week low.

Of course, no one knows when the downturn will end, but more than half of economists surveyed by The Wall Street Journal expect the Federal Reserve to begin lowering interest rates by the first quarter of 2024. At that point, economic uncertainty may dissipate, and the stock market could rebound.

However, even if that doesn't happen, investors can still find comfort in this fact: Every past bear market has eventually ended in a new bull market. That means the next bull market is almost certainly on its way. With that in mind, Airbnb and Zscaler are trading at bargain prices compared to their historical valuations, and that creates a perfect buying opportunity for patient investors.

1. Airbnb: A travel company that doesn't own rental properties

Airbnb has reimagined the travel industry. Rather than buying real estate, the company built a platform that crowdsources rental properties from more than 4 million hosts. That asset-light business model makes Airbnb more efficient and adaptable than traditional hotel operators. It can expand its inventory (i.e., onboard new hosts) faster without spending millions of dollars, and it can target its marketing efforts to quickly build supply where travel demand is highest.

Airbnb also provides a differentiated experience for guests. Listings range from suburban estates and urban flats to beachside bungalows and tropical treehouses. It can even be an inspiration engine. Airbnb recently added dozens of search categories (e.g., beach, cabin, farmhouse) that help guests discover the perfect stay, sometimes in places they would never have thought to look.

Thanks to those advantages, Airbnb is growing quickly on both the top and bottom lines. Third-quarter revenue climbed 29% to $2.9 billion, and free cash flow soared 81% to $960 million. Additionally, gross booking value -- a leading indicator of revenue growth -- climbed 31% to $15.6 billion during that quarter. That means people are still planning to travel in spite of economic uncertainty.

That said, patient investors have good reason to be optimistic about Airbnb even if growth does decelerate in the near term. Travel and tourism is one of the largest industries in the world, and Airbnb puts its addressable market at $3.4 trillion -- a figure that comprises $1.8 billion for short-term stays, $1.4 trillion for experiences, and $210 billion for long-term stays.

Currently, shares trade at 8.5 times sales, a bargain compared to the average valuation of 19.2 times sales since Airbnb went public in 2020. That price is more than reasonable, given Airbnb's past financial results and its growth opportunity. That's why this growth stock is worth buying today.

2. Zscaler: AI-powered network security and cloud protection

Cloud computing has made traditional network security architectures ineffective. Data and applications are often stored in the cloud today, so it no longer makes sense to route traffic through firewall-protected corporate data centers. Zscaler addresses that issue with its secure access service edge (SASE), a platform that employs machine learning to inspect web traffic and enforce zero-trust security policies in the cloud.

Zscaler operates the largest network security cloud in the world. On a daily basis, more than 300 trillion security signals inform its machine learning models, and each one makes its threat detection engine more effective. Management believes that advantage enables its SASE platform to offer better protection than any rival product.

In a nutshell, Zscaler creates a faster and more secure IT environment for its customers while eliminating the need for costly on-site security appliances. That value proposition has driven strong demand. Zscaler has reported a net retention rate above 125% for the last seven quarters, meaning the average customer is spending over 25% more each year. In turn, revenue soared 61% to $318 million in the most recent quarter, and free cash flow more than doubled to reach $75 million.

Going forward, investors have good reason to be optimistic. Management sees an opportunity to grow revenue from core products sixfold with current customers -- and that doesn't include newer offerings like cloud protection and digital experience monitoring. In total, the company puts its addressable market at $72 billion, and the company is well positioned to capitalize on that opportunity.

Research company Gartner has recognized Zscaler as an industry leader for 11 consecutive years. Better yet, Gartner believes SASE adoption will quadruple between 2021 and 2025. That trend should be a powerful growth driver for Zscaler, and with shares trading at 15.5 times sales -- a considerable discount to the three-year average of 37.2 times sales -- this cybersecurity stock is worth buying today.