I love a good post to post high low set. I always try to have at least one post to post high low set every game. I have scored a lot of baskets using the high low post to post pass.
A high low post to post does not have to be complex. Sometimes the simpler the setup is the easier it is to get the pass completed. The key is making sure the passing post player in the high post is good at handling the ball and making a good entry pass. A good passing post player at the high post can deliver the right located pass making it an easy basket. Likewise bad passes can make the post to post high low set very difficult to score with.

This play starts in a 1-4 High with a direct pass to the big(4). The big(4) needs to take a step up off of the foul line to create the space needed to make a good pass. If the big(4) is on the foul line, then the post to post pass becomes very difficult because their is not enough space. As a player, I liked to be on the 3-point line to make the pass. As a coach, I want the high post player to be at least in the middle between the 3-point line and foul line.

After the entry pass, the forward(3) moves down to the corner. The point(1) runs an over cut to get both the point(1) and forward(3) on the same side.
The two post players both have a job to do to make the post to post pass as easy as possible. If either post player does not do their job, then the post to post pass becomes more difficult and sometimes not possible.
First, the big(4) is going to dribble across the midline of the court. They need to clear the midline to get a good angle on the pass.
And second, the center(5) is going to move to the low post. The center(5) is going to try and push into the middle of the lane if possible. The key is to not cross the face of their defender. But the center(5) should try and push the defender towards the forward(3) as far as they can. If the center(5) can get to the midline and keep their defender on the forward(3) side of them, then the pass is very easy. If the center(5) crosses the face of their defender, then the pass is very difficult to make.
The center(5) is creating the space for the pass by getting as close to the midline as possible. If the center(5) stays on the block, then the defender still has the ability to deflect the entry pass. The space is not there to make a quality pass. The center(5) has to use their body to help push their defender into the middle of the lane.

By getting into the middle of the lane, the center(5) creates a good angle for the big(4) to make the wraparound pass into the center(5). And by getting into the middle of the lane, the center(5) has an easy catch, turn and shot on their side of the basket. By getting into the middle of the lane, the center(5) will get to use the rim to prevent their defender from blocking the shot. So, the more space the center(5) can get into the lane the easier they will have to score the ball.

If the post to post pass does not occur, then the play is not dead. The big(4) will pass across to the guard(2). Now the offense has a couple of additional options to still get a shot.

Option 1
The guard(2) has the ability to still catch and enter the ball to the center(5). The center(5) has the post to post pass but also has the chance to get a post feed from the guard(2) if the initial seal is not there on the post to post.
Option 2
The point(1) and big(4) will step down to set a stagger screen for the forward(3) to run to the top of key for a catch and shoot opportunity. This stagger screen forces the defense into a choice.
If the helpside defense drops to the post, then the stagger screen will free up the forward(3) for the 3-point shot. The stagger screen can also occupy the helpside defense giving the center(5) more freedom to make any move they want on the entry pass from the guard(2).
Quick hitters do not have to be complex. Sometimes the simpler the play is the better the offense is able to execute. A well executed simple play is much better then a poorly executed complex play. This play is easy enough for every player on offense to know exactly what they doing. By knowing exactly what they are doing the players are able to execute at a high level.