I've watched this replay once and have no idea why I lost. He has more units than me so is able to fight on multiple fronts. He also gets lucky with an early bot. I get air before him but my bombers behave stupidly. I reclaim the mushrooms in the middle which briefly sees my score higher than his. This is a really short and boring replay by the way.
You need more engies at the start and should use your ACU to build 3 pgen and airfactory before moving out. Use first and third engy to expand and reclaim and 2nd engy to build hydro/factories