Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.If you are looking to diversify your portfolio, consider Fidelity Fund (FFIDX). FFIDX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. This fund is a winner, boasting an expense ratio of 0.45%, management fee of 0.31%, and a five-year annualized return track record of 12.44%.Nationwide Growth Fund R (GGFRX). Expense ratio: 1.24%. Management fee: 0.45%. GGFRX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. This fund has managed to produce a robust 12.19% over the last five years.Janus Henderson Enterprise D (JANEX): 0.79% expense ratio and 0.64% management fee. JANEX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 11.39% over the last five years.There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk. 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 UpWant 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 Get Your Free (FFIDX): Fund Analysis Report Get Your Free (JANEX): Fund Analysis Report Get Your Free (GGFRX): Fund Analysis Report To read this article on Zacks.com click here. Zacks Investment Research