Here at Zacks, we focus on our proven ranking system, which places an emphasis on earnings estimates and estimate revisions, to find winning stocks. But we also understand that investors develop their own strategies, so we are constantly looking at the latest trends in value, growth, and momentum to find strong companies for our readers.Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use tried-and-true metrics and fundamental analysis to find companies that they believe are undervalued at their current share price levels.Luckily, Zacks has developed its own Style Scores system in an effort to find stocks with specific traits. Value investors will be interested in the system's "Value" category. Stocks with both "A" grades in the Value category and high Zacks Ranks are among the strongest value stocks on the market right now.One company value investors might notice is ProPetro Holding (PUMP). PUMP is currently holding a Zacks Rank of #2 (Buy) and a Value grade of A.We should also highlight that PUMP has a P/B ratio of 1.38. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. This stock's P/B looks attractive against its industry's average P/B of 3.49. PUMP's P/B has been as high as 1.99 and as low as 0.94, with a median of 1.33, over the past year.Finally, our model also underscores that PUMP has a P/CF ratio of 11.96. This figure highlights a company's operating cash flow and can be used to find firms that are undervalued when considering their impressive cash outlook. This stock's P/CF looks attractive against its industry's average P/CF of 17.03. PUMP's P/CF has been as high as 19.36 and as low as 8.33, with a median of 12.20, all within the past year.These are just a handful of the figures considered in ProPetro Holding's great Value grade. Still, they help show that the stock is likely being undervalued at the moment. Add this to the strength of its earnings outlook, and we can clearly see that PUMP is an impressive value stock right now. Zacks Names "Single Best Pick to Double" From thousands of stocks, 5 Zacks experts each have chosen their favorite to skyrocket +100% or more in months to come. From those 5, Director of Research Sheraz Mian hand-picks one to have the most explosive upside of all. It’s a little-known chemical company that’s up 65% over last year, yet still dirt cheap. With unrelenting demand, soaring 2022 earnings estimates, and $1.5 billion for repurchasing shares, retail investors could jump in at any time. This company could rival or surpass other recent Zacks’ Stocks Set to Double like Boston Beer Company which shot up +143.0% in little more than 9 months and NVIDIA which boomed +175.9% in one year.Free: See Our Top Stock and 4 Runners Up >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report ProPetro Holding Corp. (PUMP): Free Stock Analysis ReportTo read this article on Zacks.com click here.Zacks Investment Research