select nvewi.zone as "Zone-Type", sum(nvewi.bev) as "Inhabitants Isochrones", sum(nvewp.bev) as "Inhabitants Puffer"
from nvewi
inner join nvewp
on nvewi.zone=nvewp.zone
group by nvewi.zone

bev zone
50  a
20  a
30  a
10  b
20  b
30  b
2   c
2   c

bev zone
10  a
10  a
20  a
5   b
3   b
2   b
1   c
1   c

Zone-Type   Inhabitants Isochrones  Inhabitants Puffer
a   300 120
b   180 30
c   8   4

Zone-Type   Inhabitants Isochrones  Inhabitants Puffer
a   100 40
b   60  10
c   4   2