As asked for by Tycho_Nova. I just copied what Magma had done for the harbor.

Copy all below and paste into the bottom of Magma's districtadjacency.sql file (I recommend you open in Notepad++).

--industrial zone gets +1 production per lumbermill
insert into Adjacency_YieldChanges (
ID,
Description,
YieldType,
YieldChange,
TilesRequired,
OtherDistrictAdjacent,
AdjacentSeaResource,
AdjacentTerrain,
AdjacentFeature,
AdjacentRiver,
AdjacentWonder,
AdjacentNaturalWonder,
AdjacentImprovement,
AdjacentDistrict,
PrereqCivic,
PrereqTech,
ObsoleteCivic,
ObsoleteTech,
AdjacentResource)
values (
'INDUSTRIAL_ZONE_LUMBERMILL_PRODUCTION',--ID
'LOC_DISTRICT_LUMBERMILL_PRODUCTION',--Description
'YIELD_PRODUCTION',--YieldType
1,--YieldChange
1,--TilesRequired
0,--OtherDistrictAdjacent
0,--AdjacentSeaResource
null,--AdjacentTerrain
null,--AdjacentFeature
0,--AdjacentRiver
0,--AdjacentWonder
0,--AdjacentNaturalWonder
'IMPROVEMENT_LUMBER_MILL',--AdjacentImprovement
null,--AdjacentDistrict
null,--PrereqCivic
null,--PrereqTech
null,--ObsoleteCivic
null,--ObsoleteTech
0--AdjacentResource
);

insert into District_Adjacencies (DistrictType, YieldChangeId)
values ('DISTRICT_INDUSTRIAL_ZONE','INDUSTRIAL_ZONE_LUMBERMILL_PRODUCTION');