The Hammers - playing in front of co-owners David Sullivan and David Gold for the first time at the Boleyn Ground since their successful takeover - had plenty of possession but lacked a cutting edge in attack even after the second-half introduction of fit-again England striker Carlton Cole.
Zola hopes the imminent arrival of South Africa international McCarthy can solve that.
"It looks like it is done and next week he should be coming to train with us," Zola said of the 32-year-old.
"I do not know the terms yet, but they have told me the deal is done.
"He should be available for the next game.
"Benni will be a threat in the last third.
"He is a player who can score goals and he will be a very good help for us."
Sullivan and Gold are both life-long Hammers fans and their buy-out of a controlling interest from Icelandic bank CB Holding settled what has been a turbulent period for the east London club.
Zola added: "They have given us stability and maybe some more players to strengthen the team, and that is a good thing."
West Ham failed to get out of first gear against Rovers and on another day could have lost.
Just before the break, Morten Gamst Pedersen's 25-yard free-kick crashed against the crossbar and then substitute Jason Roberts failed to beat Robert Green when clean through with 15 minutes left.
Zola said: "I was expecting us to create a bit more quality, but we were not able to do that.
"The tension caught us a little bit, everybody was nervous and we could not express the quality we needed to break them down.
"But I take it as a good day, because this point means we step up the table."
Rovers boss Sam Allardyce believes his side could feel somewhat hard done by not to have left Upton Park with all three points.
As well as hitting the woodwork and Roberts' miss, Allardyce also pointed to two other key moments: when England goalkeeper Green pulled off a brilliant save to deny Martin Olsson and when Mark Noble appeared to handle a shock from Gael Givet before it was cleared off the line.
"We are disappointed we have not turned a very, very good second-half performance into a victory," said Allardyce.
"We had the free-kick which hit the bar, and then Jason Roberts' chance, Martin Olsson's drive is going in the top corner and Robert Green has saved it, then there is the penalty.
"The handball on the line is just one of those things you hope the referee would spot, but he has not been able to.
"What should have been a definite penalty for us wasn't, because if he has not handballed it, it was in.
"That aside, we have had enough chances to put the ball in the net more than once, and we failed to do that."
Allardyce added: "We feel a little hard done by, but in the main we should have been a bit more clinical in front of goal and would have won.
"It was a satisfying performance again, but not the right result."
Source: Team Talk
Source: Team Talk