ChessBase offers a variety of "modular" chess playing programs (called "engines"😉, but why would you need more than one chess engine? ChessCentral columnist Steve Lopez offers one reason (of many) in this article on the "Compare analysis" feature found in the Fritz and Rybka chess program interfaces.
The chess playing programs offered by ChessBase (Fritz, Rybka, Shredder, and Hiarcs) offer many features to help you improve your own chess play, but few are as (sadly) underutilized as the "Compare analysis" feature. This useful function allows multiple chess programs (called "chess engines"😉 to analyze your chess games...
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https://www.chesscentral.com/Articles.asp?ID=461
Robin Smith wrote a book about using engines for analysis (Modern Chess Analysis?) in which he recommends using at least three engines running at the same time for analysis. I think he was talking about "analysis" in the sense of what ICCF players do to find a move though, rather than post game analysis. Don't do it here or things could get unpleasant!
While the OP smacks of soliciting, I would say that Robin Smith's (RIP) book is a good read, but a bit outdated. If you are going to be playing ICCF games or are super serious about analyzing your finished games then it behooves you to understand some of the issues that engines have and how each differs causing strengths and weaknesses.