Zack is a backtesting engine built with Zig, intended for assessing trading strategies. The comments reflect a mix of interest in practical applications of backtesting, skepticism about the reliability of past data in predicting future price trends, and discussions around algorithmic trading complexities. Users express curiosity about historical data sources and share opinions on market phenomena like momentum and 'meme stocks'. There's a debate on the efficacy of algorithmic strategies in the current fast-paced market, with some suggesting that traditional investments in index funds may still be the most prudent. Additionally, the challenge of executing large trades efficiently without significant market impact is noted as an important consideration in algorithmic trading. Overall, there is a blend of enthusiasm for developing and testing strategies, tempered by concerns about the actual effectiveness and profitability of backtesting in today’s markets.