The doors and windows do not bear any weight.
Shoring brick veneer and widening the openings is not a simple job, and often requires fastening temporary supports in to the brisk while the work is completed.
This is not a simple job.

We did it all they did was use a floor jack with a board between brick and jack.Jack it up not alot,and slowly. brace it up till you get the permanant ones in.

And just how do you bear the weight at the same time you get the new lintel in?

I took out 16 foot of first story brick when I did my kichen addition. I had to support the second floor brick while installing the supports for both brick and house load. I built a temporary stud wall for the house and bolted a ledger into the studs, through the brick mortar joints. I put studs under the ledger at a slight angle to support the bricks. I installed a double LVL with a 1/2" flitch plate in the middle. A 3/8"x 4"x 16' lintel was integrated into the LVL sandwich and bolted together to hold up the brick. After the structural elements were in place I filled in the brick from the lintel to the supported brick above, about 12".
You'll do the same, just on a smaller scale.
***This should not be done if you have no concepts of house loads and how to compensate for them.***
Done incorrectly will cause injury or death. Even a few rows of brick will fracture your skull.
I'd recommend having a professional handle this aspect of the job. I am a remodeling contractor with 30 years experience. The supports were engineered by a structural engineer as part of the architectural blueprints for the job.
Ron

I add bolts about every other brick into the wall (3/8 drop in steel anchors).
I then fasten a 3 inch by 6 inch steel angle to the bricks (6 inch flat on the brick).
The angle is supported by temporary shoring based on the loads.
It may be some 2x10 with a 2x4 on edge to control bow, or heavier stuff for a 2 story wall.
Temporary footers hold the weight. A large hole with a good bed of pea greavel and some 2x lumber works most of the time.
With all the weight taken up by the shoring you can cut away any brick under the angle.
A corectly sized steel lintel (or occasinally wood) is then placed.
Any gaps betwene the bottom of the brick and the lintel is filled with mortar.
After the lintel bed and mortar have set all the shoring can be removed, the angle unbolted, and the holes filled.

It takes some work to support the brick while being able to get a new lintel in under it with no gaps and adequate support for the lintel.

Make a mistake and anything from cracks in the wall above the opening to major failure can occur.

It gets more risky with larger openings and higher walls.

I need to open two spaces in a cinderblock wall, both load bearing. The holes need to be large enough to install a 10x6 HVAC return boot. Do I need to install lintels?