Postgres- merge 2 different query results

Question

I have 3 tables table1,table2,maintable:

table1

tb1col1	tb1col2	maintable_id
abc	John	123
dof	Mat	123
cda	Mary	123
xyz	Max	687

table2

tb2col1	tb2col2	maintable_id
A	2.0	123
B	5.0	123
C	11.0	345
A	2.0	687

maintable

id	date
123	2023-09-10
345	2023-09-11

I want to merge 2 queries with below result :

tb1col1	tb1col2	tb2col1	tb2col2
abc	John	A	2.0
dof	Mat	B	5.0
cda	Mary

Ive tried select * from (select tb1col1,tb1col2 from maintable m left join table1 tb1 on tb1.maintable_id=m.id where date='2023-09-10')y full join (select tb2col1,tb2col2 from maintable m left join table2 tb2 on tb2.maintable_id=m.id where date='2023-09-10')x on y.maintable_id=x.maintable_id;

which gives me:

tb1col1	tb1col2	tb2col1	tb2col2
abc	John	A	2.0
abc	John	B	5.0
dof	Mat	A	2.0
dof	Mat	B	5.0
cda	Mary	A	2.0
cda	Mary	B	5.0

Ive also tried UNION

(select tb1col1,tb1col2,NULL as tb2col1,NULL as tb2col2 from maintable m left join table1 tb1 on (tb1.maintable_id=m.id) union all (select NULL as tb1col1,NULL as tb1col2,tb2col1,tb2col2 from maintable m left join table2 tb2 on tb2.maintable_id=m.id);

which gives me :

tb1col1	tb1col2	tb2col1	tb2col2
abc	John
dof	Mat
cda	Mary
	A	2.0
	B	5.0

But expected result is

tb1col1	tb1col2	tb2col1	tb2col2
abc	John	A	2.0
dof	Mat	B	5.0
cda	Mary