If one is playing a game of skill like poker, or black jack, he cannot play any other games because he is focused on the game. Same goes with slots, although it can be played with auto spin, it is a bit troublesome to play other game because the auto spin is suspended when there is another application in full screen in the front of computer operation.
I do not find any problem playing in multiple games. If a player is lucky, he is luck, if he is not then even with a single game play he will lose. So I don't believe that it is more effective in terms of winning to play or focus in just a single game or single kind of games.
How about betting on the few matches at the same time and also playing a casino game while awaiting the results of that bet. This can be done and i would not call it a strategy to lose. However, we do require capital to place simultaneous bets and also play a (single) casino game at the same time.
However, we cannot play few casino games at the same time as it will result in a loss (lack of dedication on each game) and also you will not find any entertainment while doing this type of gambling. Those who do this, may also not able to manage the money properly too , as they won't be able to calculate instantly as how much they won or loss and whether they are in overall profit or loss.