Stocks notched significant gains last week as both the Dow Jones Industrial Average (DJINDICES:^DJI) and the S&P 500 (SNPINDEX:^GSPC) set new all-time highs. The indexes are up roughly 12% so far this year.

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Several highly anticipated earnings reports are scheduled for the next few trading days. Here's what investors will be looking for when AutoZone (NYSE:AZO), FedEx (NYSE:FDX), and CarMax (NYSE:KMX) announce their latest business results.

AutoZone's profit forecast

AutoZone shares have significantly underperformed the market recently after the auto parts retailer surprised investors with a dramatic growth slowdown. Comparable-store sales fell into negative territory last quarter, and the company posted its weakest earnings growth in over a decade.

CEO Bill Rhodes told investors in late May 2017 that the company faces additional profit challenges over the coming quarters, including rising labor costs. Executives aren't fazed by the recent slumping comps trends, though. "We are confident in our long-term positive fundamentals for sales growth," Rhodes said.

Management noted that the last few weeks of the fiscal third quarter were marked by improving comps, so it's possible AutoZone will announce a return to growth this week. Yet the stock is likely to react more directly to management's forecast for fiscal 2018 as investors brace for a potential second straight year of unusually weak profit gains.

FedEx's profit margin

FedEx stock is near record highs heading into this week's earning release. Investors have grown more confident about the package delivery giant's business lately, especially after the company trounced earnings expectations three months ago. Factors pushing results higher right now include rising volumes, increased prices, and the integration of the TNT European delivery segment into the business.

A customer signs for a package delivery at her home.

Image source: Getty Images.

FedEx must spend aggressively to support the added volume that comes with economic growth and spiking demand for e-commerce deliveries. In fact, the company is targeting $5.9 billion of capital spending on its network this fiscal year, up from $5.1 billion last year. Management considers these modernization projects well worth the cash outlay, and investors are likely to agree given FedEx's optimistic outlook. Executives' latest forecast calls for earnings of between $12.45 per share and $13.25 per share this year -- compared to $11.07 in fiscal 2017.

CarMax's customer traffic

Used car retailer CarMax will post its fiscal second-quarter earnings results before the market opens on Friday. Its last report contained plenty of good news for investors. Used car sales volumes spiked 14% thanks to the powerful combination of rising customer traffic levels and improved conversion rates. Those trends helped drive comparable-store sales up a healthy 8% in the first quarter. At the same time, gross profit margin ticked higher and expenses fell, which allowed net income to soar by 21% to $212 million.

A smiling customer sitting in a car as the keys are handed to him.

Image source: Getty Images.

IRS tax refunds played a role in those booming results, so investors this week will be watching for evidence that CarMax can sustain its operating gains in the absence of that seasonal lift, especially as used car prices drift lower across the industry. An early sign of a weakening business would be a dip in gross profit per vehicle to below the $2,100 to $2,200 range it has managed for years. 

Assuming its comps expansion pace remains healthy, though, the retailer is likely to continue an aggressive growth strategy that's targeting 16 dealership openings this year, including in major new markets like Salisbury, Maryland, and Myrtle Beach, South Carolina.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.