Multiple keypresses can be chained with plus signs. (If you actually need the plus key, use the word "plus". Likewise, "alt", "ctrl" for those keys etc.)
The keys are still pressed in the order specified, but the --delay option changes the time between them. The manual page says the default is 12ms.
If 0 doesn't work, try 1, etc. I only tested in a Terminal and a delay of 0 was fine there, but other software may differ.