Vette, Jazz was saying that your blue gears have 6 teeth, the yellow gear has 7. IT NO WORK!
You are using 2 motors of the SAME speed rating, yet you have one motor connected to the other using DIFFERENT gear ratios, the motors WILL fight each other and any possible gains will be cancelled or made worse than if it were just a single motor. Your orange idler is an 18 to 7, just like the ZZ green.
For reference:
- Blue idler is an 18 teeth to 6 teeth (3:1 ratio).
- Green idler is an 18 teeth to 7 teeth (2.57:1 ratio)
So, 3:1 does NOT equal 2.57:1. Therefore, your motors WILL be fighting eachother, just like Jazz said.
-- EDIT
I just realized you're doing some really, um... interesting, gearing. Uh, wow.

You really don't get gear ratios do you?
Ok, let's start at the pinion of the top motor: 7 teeth
that meshes with an 18 tooth. (2.57:1 reduction)
...is mounted to a 7 tooth that meshes with an 18 tooth. (2.57:1 reduction)
...which is a motor pinion (despite the other MATCHED motor already having a 6.60:1 reduction)
Which has the 18t gear meshed with an 18t gear (1:1 ratio)
which goes into the stock blue drivetrain. 6t to 24t (4:1)
Which is really just a huge mess!
Your Top motor sees: 67.848:1
Your Bottom motor sees: 26.4:1
No, they aren't fighting eachother at all!