How many stereoisomers are possible for hepta-1,6-diene?
In the case of your original drawing with the terminal double bonds, there are no E or Z (trans or cis) isomers!



E and Z isomers are only possible if both ends of the $\ce{C=C}$ double bond each carry a substituent other than a hydrogen atom.


As far as the other structure is concerned, E and Z isomers look as follows: