My name is XXXXX XXXXX I am a sport performance specialist and CSCS with a masters degree in exercise physiology.We have to consider your age and the amount of activity you are doing because too much too soon can lead to overtraining very quickly(in every age group) and more importantly set people up for injury.So first thing is I would put squash FIRST on its own day. A lot of violent striking, abrupt stop and go, a ton of attention and energy needed - in other words it can be VERY hard on the body. The lower body can take quite a bit of time to learn to "control" the body in motion so put this by itself so you only have to worry about it. If you felt so inclined you could do some swimming after or some non(or low) impact cardio for conditioning(bike, walking, elliptical)I would put your strength training before your swimming and aerobics(perhaps alternate of the latter) because you wouldn't want fatigue to be a factor BUT you need to include a 10-15 minute warmup cardio session and including some lighter stretching before weight training. This is important because the cardio will literally warm up your tissues and stretching will help with their extensibility.Biggest thing here is, and this is important: Do NOT go 100 percent on any one of the activities during the first few weeks. You do not want to overreach in training and then be set back by lack of progress from an injury or the body just being overworked. This again goes for all populations, but more so because as we age a big, the body recovers just a little slower than when you are younger.Also, one final note - separate weight training and squash by at least 24 hours, maybe 48 just to make sure you get in adequate recover as they are probably the most physically demanding once the intensity levels get up.With all that being said and looking at your limited schedule I would alternate the intense activities simply because this is a TON of work for the body to recover from even for semi-elite younger athletes. Longevity and enjoyment is key here, we dont want you to get injured or be riding the line of recovery for the whole week only to regress in your training or progress.So cliffs notes:-Squash by itself, maybe cardio after it but WARM UP before-Weights followed by cardio-Swimming and aerobics as a form of cardio assuming the aerobics isn't super hard impact or ballistic in nature-MOST IMPORTANT: Warm up for 20 minutes of light cardio and stretching before each, stretch after each - very important.-Slowly introduce yourself to each activity as you add it for the first 3-5 weeks before going harder and getting super competitive, treat it as training and give body time to adapt completely before going hard.Good luck!