Hardcoding the _payInZRO field disallows the protocol from estimating fees when using ZRO tokens as a fee payment option (ZRO might be launching in the coming year). Consider passing the _payInZRO field as an input parameter to allow flexibility of future fee payments using ZRO. (Note: Although in the docs here, theyve mentioned to set _payInZRO to false, it is only temporarily to avoid incorrect fee estimations. Providing _payInZRO as an input parameter does not affect this since bool value by default is false).
We can also see point 6 in this integration checklist provided by the LayerZero team to ensure maximum flexibility in fee payment options is achieved. 
Here is the point (useZro is now changed to _payInZRO):
There are 2 instances of this issue:
https://github.com/code-423n4/2023-09-maia/blob/f5ba4de628836b2a29f9b5fff59499690008c463/src/RootBridgeAgent.sol#L150
Check Line 154 below:
https://github.com/code-423n4/2023-09-maia/blob/f5ba4de628836b2a29f9b5fff59499690008c463/src/BranchBridgeAgent.sol#L161C1-L173C6
Check Line 172 below:
