could zero
Regular verb: zero - zeroed- zeroed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could zero
you could zero
he could zero
we could zero
you could zero
they could zero 	I could be zeroing
you could be zeroing
he could be zeroing
we could be zeroing
you could be zeroing
they could be zeroing	I could have zeroed
you could have zeroed
he could have zeroed
we could have zeroed
you could have zeroed
they could have zeroed	I could have been zeroing
you could have been zeroing
he could have been zeroing
we could have been zeroing
you could have been zeroing
they could have been zeroing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't zero
you couldn't zero
he couldn't zero
we couldn't zero
you couldn't zero
they couldn't zero 	I couldn't be zeroing
you couldn't be zeroing
he couldn't be zeroing
we couldn't be zeroing
you couldn't be zeroing
they couldn't be zeroing	I couldn't have zeroed
you couldn't have zeroed
he couldn't have zeroed
we couldn't have zeroed
you couldn't have zeroed
they couldn't have zeroed	I couldn't have been zeroing
you couldn't have been zeroing
he couldn't have been zeroing
we couldn't have been zeroing
you couldn't have been zeroing
they couldn't have been zeroing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I zero?
could you zero?
could he zero?
could we zero?
could you zero?
could they zero? 	could I be zeroing?
could you be zeroing?
could he be zeroing?
could we be zeroing?
could you be zeroing?
could they be zeroing? 	could I have zeroed?
could you have zeroed?
could he have zeroed?
could we have zeroed?
could you have zeroed?
could they have zeroed? 	could I have been zeroing?
could you have been zeroing?
could he have been zeroing?
could we have been zeroing?
could you have been zeroing?
could they have been zeroing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I zero?
couldn't you zero?
couldn't he zero?
couldn't we zero?
couldn't you zero?
couldn't they zero? 	couldn't I be zeroing?
couldn't you be zeroing?
couldn't he be zeroing?
couldn't we be zeroing?
couldn't you be zeroing?
couldn't they be zeroing? 	couldn't I have zeroed?
couldn't you have zeroed?
couldn't he have zeroed?
couldn't we have zeroed?
couldn't you have zeroed?
couldn't they have zeroed? 	couldn't I have been zeroing?
couldn't you have been zeroing?
couldn't he have been zeroing?
couldn't we have been zeroing?
couldn't you have been zeroing?
couldn't they have been zeroing?