How do I get by this?

[Mellowmarrow]

Screenshot here:
http://puu.sh/24Zcr

The left/right sides take longer to dissolve than the top/bottom, so I connect them in two different lines, and trigger them at different times. I can get all four to be timed appropriately, but the door only opens for a split second. It closes before it's wide enough for me to run through, even if I'm standing right beside the door. The cubes respawn too quickly.

How do I get by this?

[Senen]

There are two way.
The "speedrun way" is to right-click the different lined with the good timing, like you tried to do. But it's hard.
The "usual way" is to connect the lines so that they have the same length from their beginning to the intersection, so that by right-clicking the intersection, they dissolve in the same time.